Effects of potassium antimony tartrate on rat erythrocyte phosphofructokinase activity

In an earlier study, we observed a marked accumulation of antimony in erythrocytes of rats administered potassium antimony tartrate (Sb) in drinking water. This observation has raised concerns of possible adverse effects on the hematological systems. A study was therefore carried out to investigate the effects of Sb on phosphofructokinase (PFK), a rate-limiting enzyme of erythrocyte glycolysis. Preincubation of PFK with Sb caused a marked inhibition of the enzyme with 95% loss of activity at 5 mM. In comparison, 5 mM sodium arsenite, a known enzyme inhibitor, reduced PFK activity by only 38%. Increasing the concentrations of fructose-6-phosphate (F6P) or magnesium had no effects on the inhibitory potency of Sb. Varying the concentrations of ATP and Sb produced a complex effect on PFK activity. At 1 mM ATP, 0.2 mM Sb was required for 50% inhibition (IC₅₀) of PFK but only 0.05 mM Sb was required for the same inhibition when the concentration of ATP was reduced to 0.2 mM. Glutathione (2–10 mM) and hemoglobin (8–40 <μ > M) partially protected the enzyme from the Sb effect, with the protection being more effective at low antimony concentrations. When Sb was added to assay mixtures after initiation of a PFK reaction with physiological concentrations of ATP (0.2 mM) and F6P (0.1 mM), PFK activity was approximately 50% inhibited by 0.5 mM Sb and completely inhibited by 5 mM Sb. In contrast, glucose utilization in whole blood was only 16% lower over an 8 hour incubation period in the presence of 5 mM Sb. It is concluded that while PFK is markedly inhibited by Sb under in vitro assay conditions, glycolysis in erythrocytes is not significantly affected except at very high Sb concentrations. The weak effect of Sb on glycolysis in erythrocytes may be due in part to the protective effect of hemoglobin and, to a lesser extent, glutathione on PFK. © 1998 John Wiley & Sons, Inc. J Biochem Toxicol 12: 227–233, 1998     

A mechanism for self-inhibition of population growth in the flatworm Mesostoma ehrenbergii (Focke)

Summary By producing subitaneous eggs the rhabdocoel Mesostoma ehrenbergii may quickly increase the population size. The production of this kind of eggs by young worms is inhibited by the presence of adults in the culture medium. The inhibition is specific, and it is observed also if young and adult worms are not in direct contact, or if young worms are added to the water where adults had been previously kept: there is therefore evidence for a chemical mediator. The sensitivity to the inhibition occurs during the first five days after birth, with a maximum on the 2nd to 3rd day.     

Studies on metabolism of lung fluke genus Paragonimus. VII. Action of bithionol on glycolytic and oxidative metabolism of adult worms

The present study was carried out in order to obtain information on the mechanism of action of bithionol on Paragonimus westermani (Kerbert 1878). Bithionol stimulated lactic acid production of intact adult worms above the level of the control worms, while it inhibited oxygen consumption of intact adult worms in vitro. Bithionol treatment of adult worms in vivo decreased glycolytic and oxidative metabolism of homogenates of uterine eggs and adult worms.Bithionol inhibited lactic acid formation except when fructose 1, 6-diphosphate (FDP) was used as a substrate in the homogenates of adult worms, and it also inhibited oxygen consumption of homogenates of eggs and adult worms. Bithionol inhibited reduction of methylene blue when succinate was used as a substrate. Bithionol inhibited oxidation of reduced cytochrome c in the 1000g supernatant of homogenates of adult worms. Bithionol inhibited activity of the succinate oxidation in homogenates of adult worms.     

Development of simultaneous resistance in Ostertagia circumcincta to thiabendazole, morantel tartrate and levamisole

Le Jambre L.F., Southcott W.H. and Dash K.M. 1978. Development of simultaneous resistance in Ostertagia circumcincta to thíabendazole, morentel tartrate and levamisole. International Journal for Parasitology8: 443–447. A field strain of Ostertagia circumcincta was divided into five strains based on anthelmintic selection in the laboratory. The first strain was selected with 50 mg/kg thiabendazole, the second with 4 mg/kg morantel tartrate, the third with 3.2 mg/kg levamisole, the fourth was not selected and the fifth strain was selected with all three anthelmintics in each generation. The present paper reports the dose response of the eighth generation of the multi-selected strain to thiabendazole, morantel tartrate and levamisole and compares these results with those from the eighth generation of the single selected and unselected strains.In adult O. circumcincta the LD₉₅ for thiabendazole, morantel tartrate and levamisole was 172.0, 9.2 and 8.4 mg/kg respectively in the multiselected strain, compared with corresponding values of > 200, 6.1 and 6.9 for the single selected strains and 14.5, 2.8 and < 1.6 in the unselected parent strain.Multiple selection with three anthelmintics was associated with an increase in O. trifurcata from less than 0.1 % in the unselected strain to 16% in the multi-selected strain.An increase in inhibition was a feature of both multiple selection and selection by levamisole alone. The parent strain had less than 0.1 % inhibition but the incidence increased to 16% in the levamisole selected strain and to 2% in the multi-selected strain. Approximately 8% of the inhibited larvae in the levamisole selected strain were resistant to dose levels of levamisole from 1.6 to 8.0 mg/kg. Resistance in inhibited larvae was further enhanced in the multi-selected strain and after eight generations 100% of larvae in this strain were resistant to all dose levels up to 100 mg/kg thia-bendazole, 20 mg/kg morantel tartrate and 8 mg/kg levamisole. Apparently when selected with anthelmintics that are less effective against larvae than adults, O. circumcincta responds by increasing the percentage and resistance of inhibited larvae.     

Resistance of selected lines of Haemonchus contortus to thiabendazole, morantel tartrate and levamisole.

A field strain of Haemonchus contortus isolated from sheep at Armidale N.S.W., was found to be resistant to thiabendazole with approximately 20 per cent of the worms surviving a 50 mg/kg dose. The isolate was selected over six generations for resistance to 50 mg/kg thiabendazole. After this time, selection on one line was continued at 50 mg/kg thiabendazole and selection on a second line was extended to include 8·8 mg/kg morantel tartrate. A drug tolerance assay on the third generation of the thiabendazole-morantel tartrate selected line showed the ld_5o to be 5·3 mg/kg and the ld₉₅ to be 18 mg/kg morantel tartrate; the reported ld₅₀ and ld₉₅ for non-resistant strains of H. contortus to morantel tartrate are 2·5 mg/kg and 8 mg/kg respectively. In the fourth generation the thiabendazole and the thiabendazole-morantel tartrate selected lines together with a recently isolated field strain were assayed for resistance to thiabendazole, morantel tartrate and levamisole. The results indicated that the resistance to thiabendazole was probably due to a single gene. Both selected lines were more resistant to thiabendazole than the field strain. The thiabendazole-morantel tartrate selected line was more resistant to morantel tartrate than either of the other two. Resistance to morantel tartrate appeared to be polygenic in nature and due to increased vigour. The lowest dose of levamisole (1·6 mg/kg) killed more than 95 per cent of all strains of worms. There was no significant increase in effectiveness at higher dose rates indicating that surviving worms were resistant to the drug.     

Studies on metabolism of lung flukes of the genus Paragonimus. VI. Succinoxidase system in homogenates of eggs, larvae, and adults

The present study was concerned with the succinoxidase system in Paragonimus westermani, Paragonimus ohirai, and Paragonimus miyazakii. Potassium cyanide inhibited the motility of larval and adult forms. Succinate stimulated the reduction of methylene blue by homogenates of embryonated eggs, larvae, and adults, while malonate inhibited the reduction. Reduced cytochrome c was oxidized by the 1,000g supernatant from homogenates of embryonated eggs, larvae, and adults. The supernatant prepared from unembryonated eggs did not oxidize reduced cytochrome c. Succinate stimulated oxygen consumption by the homogenate of adult worms. Oxygen consumption markedly increased in the homogenate of adults when both succinate and cytochrome c were added as substrate to the reaction mixture, while malonate and cyanide inhibited oxygen consumption.     

Cytosolic phosphofructokinase from spinach leaves : I. Purification, characteristics, and regulation

Cytosolic ATP-dependent phosphofructokinase (PFK) from spinach leaves (Spinacia oleracea L.) was enriched 2600-fold by (NH₄)₂SO₄ fractionation, DEAE anion exchange chromatography, Blue Sepharose CL-6B, and ATP agarose type 3-affinity chromatography. The final preparation had a specific activity of 417 nkat per milligram protein and exhibited four bands between 50 and 70 kilodaltons following denaturing electrophoresis. Only one band of ATP- and fructose 6-phosphate (F-6-P)-dependent, Pistimulated activity was detected following isoelectric focusing PAGE and nondenaturing discontinuous PAGE of the final preparation. Crude extracts contained, in addition to the band observed in the final preparation, a second band that was inhibited by Pi. The latter band is presumably chloroplastic PFK. PFK was stimulated by the anions Pi²⁻, Cl⁻, SO₄²⁻, NO₃⁻, HAsO₄²⁻, and HCO₃⁻ but was not affected by NH₄⁺. Pi and Mg²⁺ changed the response of PFK toward pH and affected the saturation kinetics of F-6-P. In general, activity was highest when Pi was high and (or) Mg²⁺ was low. Phosphoenolpyruvate (PEP), 2-PGA, and PPi, but not 3-PGA, inhibited PFK. Although the inhibition by PEP and 2-PGA was reduced or relieved by Pi, the inhibition by PPi was not affected by Pi. F-2, 6-P₂ had no effect upon the activity of PFK. It is proposed that, in the cytosol of spinach leaves, PFK is likely to be more active during the dark, when cytosolic Pi levels are high, than in the light.     

Phosphofructokinase from lycopersicon esculentum fruits-II. Changes in the regulatory properties with dissociation

The regulatory properties of PFK. from the tomato are discussed in relation to the dissociation of the oligomeric form of the enzyme. Both the oligomeric and monomeric forms of PFK were inhibited by citrate, malate, PEP, 2-phosphoglycerate, phosphoglycolate and ammonium sulphate. PEP was the most potent inhibitor of PFK activity with 9 and 10 μn PEP causing 50%, inhibition of the oligomeric and monomeric forms of PFK respectively. The inhibition by all these metabolites of the oligomeric form of PFK was sigmoidal while their inhibition of the monomeric form was hyperbolic. The magnitude of inhibition by these metabolites is affected by the levels of Mg²⁺. The oligomeric form of the enzyme is more resistant to citrate inhibition than the monomeric form. In the presence of citrate or ammonium sulphate, the kinetics of the oligomeric form of PFK with F6P yielded positive cooperativity while in their absence, the kinetics revealed negative cooperative interactions. Phosphoenolpyruvate had no effect on the nature of the kinetics with F6P. ADP is stimulatory to the oligomeric form while it is slightly inhibitory to the monomeric form. The significance of these properties and their relation with the regulation of PFK activity in vivo are discussed.     

Resistance of selected lines of Ostertagia circumcincta to thiabendazole, morantel tartrate and levamisole

Le Jambre I. F., Southcott W. H. and Dash K. M. 1977. Resistance of selected lines of Ostertagia circumcincta to thiabendazole, morantel tartrate and levamisole. International Journal for Parasitology7: 473–479. A strain of Ostertagia circumcincta was isolated from a field in which all sheep had been treated in sequence every 7–10 days from September 1970 to January 1974 with either thiabendazole, morantel tartrate or levamisole. Thiabendazole had not been used after the first 15 months. The LD₉₅ for this strain was 88 mg/kg thiabendazole, 6.9 mg/kg morantel tartrate and 5-4 mg/kg levamisole.Another strain of O. circumcincta isolated from an area where anthelmintics had been used much less frequently was divided into four lines for exposure to selection in the laboratory. The first line was selected with 50 mg/kg thiabendazole, the second with 5 mg/kg morantel tartrate, and the third with 3.2 mg/kg levamisole; the fourth line was not selected for drug resistance. After eight generations the three lines selected with thiabendazole, morantel tartrate and levamisole had (Spld)(in95) of > 200, 5.7 and 6.2 mg/kg for the selecting drugs respectively, compared with corresponding values of 20, 2.9, and 1.8 in the unselected line. That is, the field strain had about the same levels of resistance to morantel tartrate and levamisole as the respective laboratory strains selected with these individual drugs. However, the field strain, which had been exposed to thiabendazole for only 15 months, was less resistant to thiabendazole than the laboratory strain selected with this drug. These results show that giving of several drugs in sequence cannot be relied upon to prevent the development of resistance to the individual drugs.The dose responses of adult worms showed low, but significant resistances to morantel tartrate and levamisole and a relatively high resistance to thiabendazole. Levamisole was found to select for inhibition of development with approx. 8.0% of the inhibited larvae showing no dose response above 1.6 mg/kg. Levamisole was also associated with an increase from 0.1 % to 9.0% in the O. trifurcata component of an Ostertagia population.     

Effects of 5-hydroxytryptamine, cyclic AMP, AMP, and fructose 2,6-bisphosphate on phosphofructokinase activity in Hymenolepis diminuta

1. 5-HT (10(-4) M) had no effect on the activity of phosphofructokinase in Hymenolepis diminuta. Concentrations of ATP above 33 microM inhibited PFK activity; AMP and cyclic AMP relieved this inhibition. 2. Local levels of cyclic AMP may be indirectly modulated by NaF, guanylyl imidophosphate, or 5-HT in the presence of GTP, which stimulates adenylyl cyclase activity x2 in H. diminuta homogenates. 3. Fructose 2,6-bisphosphate (F2BP), a physiological regulator of PFK activity in rat liver, also relieved ATP-induced inhibition of PFK. F2BP was present in supernatants from the worms at about 20 mumol/g wet wt. 4. 5-HT may cause an increase in the rate of glycolysis in H. diminuta by elevating either cyclic AMP and/or AMP levels; these nucleotides can in turn increase PFK activity.     

Dipetalonema viteae: Response of spleen cells in experimental mouse filariasis to mitogens and antigens

Balb/c mice were infected by transplanting 3, 5, 10, or 20 female adult Dipetalonema viteae under the dorsal skin. The microfilaremias resulting from infections with 3 or 5 adult worms were of lesser magnitude and of shorter duration than those produced in infections with 10 or 20 worms. Spleen cells taken from these mice at various intervals after infection were assayed in vitro for their ability to respond to phytohemagglutinin (PHA) or lipopolysaccharide (LPS). There was no depression in the response to LPS or to PHA in mice given infections of 3 or 5 D. viteae adult worms. In contrast, the response to PHA was significantly depressed in groups receiving 10 or 20 adult female worms 12 days after infection and by Day 25, the depression was severe. Thereafter the PHA responsiveness recovered gradually to reach control values on Day 60. In mice transplanted with 10 or 20 D. viteae adult worms there was no significant depression in the response to LPS at any time during the infection, but the response was increased slightly sporadically during infection. These results indicate that in mice, this infection causes an initial suppression in the function of PHA-sensitive T cells but has little effect on the B cells which respond to LPS. A factor present in serum taken on Day 25 from mice infected with 10 or 20 adult worms inhibited the proliferative response to PHA by spleen cells from normal mice. The recovery of PHA responsiveness in mice given the heavier infections coincided with death of the adult worms, but mitogen reactivity and microfilaremia were unrelated. Antigens from male or female worms induced cell division in spleen cells taken from infected mice after microfilaremia had ceased whether they were implanted with 3 or 10 adult worms.     

Trichinella spiralis: mediation of the intestinal component of protective immunity in the rat by multiple, phase-specific, antiparasitic responses.

Rats infected orally with Trichinella spiralis developed an immunity that was induced by and expressed against separate phases of the parasite's enteral life cycle. Infectious muscle larvae generated an immune response (rapid expulsion) that was directed against the very early intestinal infection and resulted in the expulsion of worms within 24 hr. This response eliminated more than 95% of worms in an oral challenge inoculum. Developing larvae (preadults) also induced an immune response that was expressed against adult worms. The effect on adults was dependent upon continuous exposure of worms to the immune environment throughout their enteral larval development. Immunity induced by preadult T. spiralis was not expressed against adult worms transferred from nonimmune rats. While adult worms were resistant to the immunity engendered by preadults they induced an efficient immunity that was autospecific. Both “preadult” and “adult” immunities were expressed in depression of worm fecundity as well as in the expulsion of adults from the gut. However, the two reactions differed in respect to their kinetics and their efficiency against various worm burdens. Preadult immunity was directed mainly against fecundity whereas adult immunity favored worm expulsion. All responses (rapid expulsion, preadult and adult immunity, and antifecundity) acted synergistically to produce sterile immunity against challenge infections of up to 5000 muscle larvae. These findings indicate that the host protective response to T. spiralis is a complex, multifactorial process that operates sequentially and synergistically to protect the host against reinfection.     

Schistosomatium douthitti: carbohydrate metabolism in the adults.

Pathways of carbohydrate metabolism in the adults of Schistosomatium douthitti: were investigated. Histochemical reactions for adenosinetriphosphatase (EC 3.6.1.3) glucose 6-phosphate dehydrogenase (EC 1.1.1.49), phosphogluconate dehydrogenase (EC 1.1.1.43), glycerol-3-phosphate dehydrogenase (EC 1.1.1.8), lactate dehydrogenase (EC 1.1.1.27, 1.1.2.3) isocitrate dehydrogenase (EC 1.1.1.41), succinate dehydrogenase (EC 1.3.99.1), malate dehydrogenase (EC 1.1.1.37), cytochrome oxidase (EC 1.9.3.1), and adenosine triphosphatase (EC 3.6.1.3) were found in the adult worms. Glycogen deposits occurred in the parenchyma.Low oxygen tension immobilized the worms. Tartar emetic, sodium cyanide reduced adult motility in vitro. Manometric experiments demonstrated a respiratory quotient of approximately one. Oxygen uptake was completely inhibited by tartar emetic and partially inhibited by sodium fluoracetate and sodium cyanide. Inhibition by sodium fluoroacetate was partially counteracted by citric acid in the medium.Adults demonstrated an oxygen debt following anaerobic incubation. A maximum of 52% of the glucose consumed under aerobic conditions was excreted as lactic acid. Under anaerobic conditions the amount of lactic acid excreted increased. Acids other than lactic acid were also released. Results indicate that although glycolysis is the major pathway, two additional aerobic pathways also exist, one which is cyanide sensitive and the other cyanide insensitive.     

Purification and characterization of phosphofructokinase of Bacillus licheniformis

The phosphofructokinase (PFK) of Bacillus licheniformis was purified about 50–65-fold and examined for a number of enzymatic and physical characteristics. The enzyme is quite unstable under normal assay conditions, but Mg²⁺, K⁺, adenosine-5′-diphosphate, phosphoenolpyruvate (PEP), and fructose-6-phosphate (fru-6-P) are fairly effective stabilizing agents. Saturation functions for ATP and fru-6-P were hyperbolic. Several attempts to induce positive cooperative binding of fru-6-P were unsuccessful. However, “sigmoidal” saturation kinetics for fru-6-P could be observed under assay conditions that permitted an irreversible inactivation of the PFK during assay. Several divalent cations could support the catalysis of B. licheniformis PFK and the enzyme was activated by both NH₄⁺ and K⁺ ions. B. licheniformis PFK is inhibited by citrate, ATP, PEP, Ca²⁺, and several other metabolic intermediates, but the inhibition caused by citrate and ATP at high fru-6-P concentration and by calcium can be relieved by Mg²⁺ addition while PEP inhibition is specifically relieved by fru-6-P. There are at least three binding sites for PEP on the PFK molecule. The active form of this PFK has a molecular weight of about 134,000 daltons. In the presence of Mg²⁺, adenosine-5′-triphosphate (ATP), and PEP, at 0 °C, the PFK molecule is rapidly dissociated to an inactive form with a molecular weight of about 68,000 daltons. Association of these subunits to yield the active form of PFK occurs spontaneously, and rapidly, when the temperature is raised to 30 °C. Ninety percent of the original activity is recovered after activation. Growth of B. licheniformis on several different substrates resulted in minor variations of PFK activity. In a parallel fashion, sporulation involved no irreversible inactivation of PFK and the level of the activity was about the same throughout the life cycle. Control of this enzyme during sporulation could be affected by any or all of the cell constituents found to regulate PFK activity in vitro, but it is considered likely that the most significant in vivo negative effector is PEP, with this inhibition being reversed by fru-6-P.     

Cytosolic Phosphofructokinase from Spinach Leaves : II. Affinity for Mg and Nucleoside Phosphates

Cytosolic ATP-phosphofructokinase (PFK) from spinach leaves (Spinacia oleracea L.) was inhibited by submillimolar concentrations of free Mg²⁺. The free Mg²⁺ concentration required for 50% inhibition of PFK activity was 0.22 millimolar. Inhibition by free Mg²⁺ was independent of the MgATP²⁻ concentration. Inorganic phosphate (Pi) reduces the inhibition of PFK activity by Mg²⁺. Free ATP (ATP⁴⁻) also inhibits PFK activity. For free ATP the inhibition of PFK activity was dependent on the MgATP²⁻ concentration. Fifty percent inhibition of PFK activity requires 1.2 and 3.7 millimolar free ATP at 0.1 and 0.5 millimolar MgATP²⁻, respectively. It was proposed that free ATP competes for the MgATP²⁻ binding site, whereas free Mg²⁺ does not. Pi diminished the inhibitory effect of free ATP on PFK activity. Free ATP and Pi had substantial effects on the MgATP²⁻ requirement of cytosolic PFK. For half-maximum saturation of PFK activity 3 and 76 micromolar MgATP²⁻ was required at 0.007 and 0.8 millimolar free ATP in the absence of Pi. At 5 and 25 millimolar Pi, half-maximum saturation was achieved at 9 and 14 micromolar MgATP²⁻. PFK activity was inhibited by Ca²⁺. The inhibition by Ca²⁺ depends upon the total Mg²⁺ concentration. Fifty percent inhibition of PFK activity required 22 and 32 micromolar Ca²⁺ at 0.1 and 0.2 millimolar Mg²⁺, respectively. At physiological concentrations of about 0.5 millimolar free Mg²⁺, Ca²⁺ would have little effect on cytosolic PFK activity from spinach leaves. PFK is not absolutely specific for the nucleoside 5′-triphosphate substrate. Besides MgATP²⁻, MgUTP²⁻, MgCTP²⁻, and MgGTP²⁻ could be used as a substrate. All four free nucleotides inhibit PFK activity. The physiological consequences of the regulatory properties of cytosolic PFK from spinach leaves will be discussed. A model will be introduced, in an attempt to describe the complex interaction of PFK with substrates and the effectors Mg²⁺ and Pi.     

Strongyloides venezuelensis: heparin-binding adhesion substances in immunologically damaged adult worms

Immunologically damaged Strongyloides venezuelensis adult worms were examined for their mucosal invasion ability and secretion of heparin-binding adhesion substances. S. venezuelensis was expelled from male Wistar rats 4 to 5 weeks after infection. Four-week-old adult worms were smaller and had fewer eggs than 1-week-old adult worms. One-week-old, 4-week-old, and 5-week-old adult worms equally established in the recipient mouse intestine when surgically implanted. Adult worms of 4 and 5 weeks of age secreted adhesion substances as much as 1-week-old adult worms. There was no difference in the heparin-binding activities and the lectin-binding profile of adhesion substances among adult worms of different ages. The rate of secretion of adhesion substances from the mouth was also identical. Heparin-binding activities were detected in crude adult worm proteins; however, proteins of 5-week-old adult worms had weaker heparin-binding activities than those of 1-week-old adult worms. Western blotting revealed that a number of heparin-binding proteins were lost in 5-week-old adult worms. A heparin-binding protein of 42. 0 kDa, which was consistently expressed in adult worms, was a possible component of heparin-binding adhesion substances which are secreted from the mouth.     

Identification and characterisation of microRNAs in young adults of Angiostrongylus cantonensis via a deep-sequencing approach

Angiostrongylus cantonensis is an important causative agent of eosinophilic meningitis and eosinophilic meningoencephalitis in humans. MicroRNAs (miRNAs) are small non-coding RNAs that participate in a wide range of biological processes. This study employed a deep-sequencing approach to study miRNAs from young adults of A. cantonensis. Based on 16,880,456 high-quality reads, 252 conserved mature miRNAs including 10 antisense miRNAs that belonging to 90 families, together with 10 antisense miRNAs were identified and characterised. Among these sequences, 53 miRNAs from 25 families displayed 50 or more reads. The conserved miRNA families were divided into four groups according to their phylogenetic distribution and a total of nine families without any members showing homology to other nematodes or adult worms were identified. Stem-loop real-time polymerase chain reaction analysis of aca-miR-1-1 and aca-miR-71-1 demonstrated that their level of expression increased dramatically from infective larvae to young adults and then decreased in adult worms, with the male worms exhibiting significantly higher levels of expression than female worms. These findings provide information related to the regulation of gene expression during the growth, development and pathogenesis of young adults of A. cantonensis.     

Comparison of phosphofructokinases in submandibular glands of immature and adult rats

1. Phosphofructokinases (PFKs) in immature and adult rat submandibular glands were purified to near homogeneity, and their properties were compared. 2. PFK in immature gland was less sensitive to inhibition by ATP than adult PFK. 3. Saturation curve for fructose 6-phosphate of PFK in immature gland was less sigmoidal than that of adult PFK indicating the lower cooperativity of subunits in immature PFK. 4. Fructose 2,6-bisphosphate relieved PFK from inhibition by ATP in adult gland, but a similar effect was not clearly observed in immature gland PFK. 5. Adult PFK was a heterotetramer consisting of C-, M-, L-subunits, but in immature PFK another type of subunit, which was slightly smaller than L-subunit, existed in addition to C-, M- and L-subunits.     

Shifts in the Distribution of Mass Densities Is a Signature of Caloric Restriction in Caenorhabditis elegans

Although the starvation response of the model multicellular organism Caenorhabditis elegans is a subject of much research, there is no convenient phenotypic readout of caloric restriction that can be applicable to large numbers of worms. This paper describes the distribution of mass densities of populations of C. elegans, from larval stages up to day one of adulthood, using isopycnic centrifugation, and finds that density is a convenient, if complex, phenotypic readout in C. elegans. The density of worms in synchronized populations of wildtype N2 C. elegans grown under standard solid-phase culture conditions was normally distributed, with distributions peaked sharply at a mean of 1.091 g/cm³ for L1, L2 and L3 larvae, 1.087 g/cm³ for L4 larvae, 1.081 g/cm³ for newly molted adults, and 1.074 g/cm³ at 24 hours of adulthood. The density of adult worms under starvation stress fell well outside this range, falling to a mean value of 1.054 g/cm³ after eight hours of starvation. This decrease in density correlated with the consumption of stored glycogen in the food-deprived worms. The density of the worms increased when deprived of food for longer durations, corresponding to a shift in the response of the worms: worms sacrifice their bodies by retaining larvae, which consume the adults from within. Density-based screens with the drug Ivermectin on worms cultured on single plates resulted in a clear bimodal (double-peaked) distribution of densities corresponding to drug exposed and non-exposed worms. Thus, measurements of changes in density could be used to conduct screens on the effects of drugs on several populations of worms cultured on single plates.     

Chemical composition of newborn larvae, muscle larvae and adult Trichinella spiralis

Chemical composition of newborn larvae, muscle larvae and adult Trichinella spiralis. International Journal for Parasitology16: 455–460. The chemical composition of newborn larvae (NBL), muscle larvae (ML) and 4-day-old and 7-day-old adult Trichinella spiralis were compared. Total protein constituted 44.1% of the dry wt of ML, 36.9% of NBL and 30.3% of 7-day-old adult worms. Glycogen content was 16.1% of worm dry wt in ML and 7.8% in NBL and 7.2% of worm dry wt in adults. Trehalose content was 5.2% in NBL, 8.3% in ML and 8.7% in 7-day-old adult worms. Significantly lower levels of trehalose and glycogen were found in 4-day-old worms than were present in 7-day-old worms. Free glucose amounted to 0.1% of dry wt in ML, 0.37% in NBL and 0.87% in 7-day-old adults. RNA accounted for 3.5% of the dry wt of ML, 3.2% of the dry wt of 7-day-old adults and 1.1% of the dry wt of NBL. The DNA content of NBL was 0.23% of worm dry wt, in ML 0.48% of worm dry wt and 0.51% of worm dry wt in 7-day-old adults. The three parasite stages examined agreed closely with regard to types of amino acids in the free pool. Exceptions were as follows: NBL lacked taurine which both adults and ML contained; adults lacked methionine which both ML and NBL contained; and, trace amounts of cysteine were present in ML but absent from the other two stages.