Salt stress differentially regulates mobilisation of carbon and nitrogen reserves during seedling establishment of Pityrocarpa moniliformis

Seedling establishment is a critical step in environment colonisation by higher plants that frequently occurs under adverse conditions. Thus, we carried out an integrated analysis of seedling growth, water status, ion accumulation, reserve mobilisation, metabolite partitioning and hydrolase activity during seedling establishment of the native Caatinga species Piptadenia moniliformis (Benth.) Luckow & R.W. Jobson under salinity. Two-day-old seedlings were cultivated in vitro for 4 days in water agar (control) or supplemented with 50 or 100 mm NaCl. Biochemical determinations were performed according to standard spectrophotometric protocols. We found that 100 mm NaCl stimulated starch degradation, amylase activity and soluble sugar accumulation, but limited storage protein hydrolysis in the cotyledons of P. moniliformis seedlings. Although Na⁺ accumulation in the seedling affected K⁺ partitioning between different organs, it was not possible to associate the salt-induced changes in reserve mobilisation with Na⁺ toxicity, or water status, in the cotyledons. Remarkably, we found that starch content increased in the roots of P. moniliformis seedlings under 100 mm NaCl, probably in response to the toxic effects of Na⁺ . The mobilisation of carbon and nitrogen reserves is independently regulated in P. moniliformis seedlings under salt stress. The salt-induced delay in seedling establishment and the resulting changes in the source-sink relationship may lead to storage protein retention in the cotyledons. Possibly, the intensification of starch mobilisation in the cotyledons supported starch accumulation in the root as a potential mechanism to mitigate Na⁺ toxicity.

Accumulation and distribution of lead in the archiacanthocephalan Moniliformis moniliformis from experimentally infected rats

It recently became clear that adult eo- and palaeacanthocephalans parasitizing fish can bioconcentrate several heavy metals to significantly higher concentrations than the tissues of their definitive hosts. Following this discovery the lead accumulation of the archiacanthocephalan Moniliformis moniliformis was investigated using experimentally infected male Wistar rats of the CD-M-strain. The worms were allowed to grow up for 4 weeks post-infection followed by a 3 weeks oral lead exposure of the rats. After the exposure period the rats were killed and the metal levels were determined in muscle, liver, intestine and kidney of the rats as well as in different organs of female and male acanthocephalans. Lead concentrations were found to be highest in female M. moniliformis followed by the kidneys of the rats. Male worms contained approximately the same lead concentration as the hosts' kidneys. Lead analysis of the worms' organs revealed the highest lead concentration in the eggs of female acanthocephalans, followed by the cement gland of male Worms. Whilst the lead burden of the presoma was higher than that detected in the kidneys of the rats, the lead content of the metasoma was even lower than in the kidneys. A lead uptake of M. moniliformis from the intestinal lumen of the host became apparent as the faeces of infected rats contained significantly less lead compared to the uninfected conspecifics. Thus, this study reveals that lead accumulation also occurs in archiacanthocephalans parasitizing mammals. But the degree of metal bioconcentration is considerably lower compared to eo- and palaeacanthocephalans in fish. Anyway, due to a lack of adequate sentinel species in terrestrial biotopes the host-parasite system rat M. moniliformis appears to be a useful and promising bioindication system especially in urban ecosystems in temperate regions.

Cadmium accumulation in Moniliformis moniliformis (Acanthocephala) from experimentally infected rats

The accumulation of cadmium in Moniliformis moniliformis parasitizing experimentally infected rats that had been orally exposed to cadmium was investigated in this study. Cadmium accumulation in the helminth and in different tissues of the host was determined using electrothermal atomic absorption spectrometry (AAS) after a 3-week period of exposure. The mean cadmium concentration measured in M. moniliformis was 5.8 microg g(-1) wet weight, which was 20, 23, and 119 times higher than that determined in the kidney, liver, and intestine of the host, respectively. Although female worms accumulated higher amounts of cadmium than did males, no tendency emerged between the cadmium concentration and the weight of individual acanthocephalans. This study reveals that cadmium accumulation also occurs in archiacanthocephalans, but to a lesser degree than in palaeacanthocephalans parasitizing fish. Due to its cadmium-accumulation capacity, M. moniliformis might be used as a highly sensitive free-living bioindicator in terrestrial and urban ecosystems.

Water balance and its relation to fermentation acid production in the intestinal parasites Hymenolepis diminuta (Cestoda) and Moniliformis moniliformis (Acanthocephala)

Water balance and its relation to carbohydrate metabolism was examined in Hymenolepis diminuta in parallel with the putative osmoconformer Moniliformis moniliformis. Worms were removed from rat intestines, weighed, and incubated (37 C) 1 hr in rat serum and various salines, some with mannitol to vary osmotic concentration from 150 to 400 mOsm/L. Worms were removed at 15-min intervals, weighed, and returned to the test solution. Rat serum and a Ringer's saline (pH 7.4 and 300 mOsm/L) with or without 5 mM glucose were isotonic to M. moniliformis, which behaved like an osmometer, shrinking, or swelling in proportion to external osmotic changes. Hymenolepis diminuta rapidly lost 20-25% wet weight in these solutions and regained lost water when 5 mM glucose was added to the saline. Tapeworms maintained constant body weight between 210 and 335 mOsm/L, but they rapidly gained or lost water outside of this range. Glucose metabolism and uptake of [3H]glucose from the medium increased progressively between 210 and 310 mOsm/L, whereas uptake rates of [3H]leucine, 22Na+, and 36Cl- were not affected. Unbuffered saline (initial pH 6.5 and 300 mOsm/L) had a lower pH (5.0) and higher osmolality (307 mOsm/L) after a 1-hr incubation with tapeworms. Such saline was less hypertonic than unconditioned saline to freshly obtained worms. A Ringer's saline (300 mOsm/L) containing 50 mM acetate- was also hypertonic (greater than 20% weight loss) to tapeworms at pH 7.4, but it was hypotonic (greater than 20% weight gain) at pH 5.0. Isotonicity at 300 mOsm/L was achieved with pH 5.0 and 20 mM acetate-, the approximate pH and fermentation acid concentration in an infected rat intestine. Rats infected with tapeworms (12 days old) were fasted for 2 days. Starved worms were smaller but had the same percentage of body water and internal osmolality as controls. These results show that H. diminuta can regulate its body water content and that water balance is closely related to the fermentation acid concentration and pH of the bathing medium.

Features of amino acid metabolism in Moniliformis moniliformis (Acanthocephala) in vitro

Experiments to investigate the metabolism of glycine, L-glutamic acid and L-aspartic acid by Moniliformis moniliformis were carried out by incubating adult worms aerobically for 3 h at 37 degrees C in Tyrode's solution containing either [U-14C]glycine, L-[U-14C]glutamic acid, L-[U-14C]aspartic acid or L-[4-14C]aspartic acid. Much of the glycine and glutamic acid was absorbed by the worms, but little of either was metabolized. Aspartic acid was readily taken up and metabolized. After incubating with L[U-14C]aspartic acid, most radioactivity was found in ethanol and a volatile compound, presumed to be carbon dioxide, with smaller amounts in lactate, alanine, acetate, malate, glucose and succinate. After incubating with L-[4-14C]aspartic acid, most radioactivity was found in lactate and the presumed CO2 with small amounts in alanine, malate and succinate. No radioactivity was found associated with ethanol or acetate. Possible metabolic pathways and suggestions for a relationship between the metabolism of aspartate with that of alanine and serine in this parasite are discussed.

Linked metabolism of L-serine and L-alanine by Moniliformis moniliformis (Acanthocephala) in vitro

Experiments to investigate the linked metabolism of L-serine and L-alanine by Moniliformis moniliformis in vitro were carried out by incubating adult worms aerobically for 3 h at 37 degrees C in Tyrode's solution containing L-[U-14C]alanine and other amino acids. When present in the medium alone, alanine was totally removed by the worms and metabolized almost entirely to ethanol and a compound identified as carbon dioxide. When present in the medium with serine and no other amino acids, alanine was largely metabolized as before but additional alanine, believed to originate from serine, was excreted. The same results were obtained with serine and 16 other amino acids in the incubation medium.

Selective metabolism of L-serine by Moniliformis (Acanthocephala) in vitro

In a series of in vitro experiments, adult male and female Moniliformis dubius were incubated at pH 6.88 and 37 degrees C for 3 h in a 2.5 mM solution of 18 amino acids. Fifteen of these were absorbed slightly from the medium, but L-serine was almost completely absorbed while the concentrations of glycine and alanine in the medium increased during the course of the incubation. By using L-[U-14C]serine, it was found that labelled ethanol and CO2 were the main end-products of metabolism excreted into the medium, with smaller amounts of labelled alanine, lactate and acetate. Small amounts of cystathionine with high specific radioactivity were found in extracts of the worms at the end of incubation, together with other radioactive metabolites including glucose, ethanol, lactate, succinate, malate, serine, glycine and alanine. Ammonia was found to be an excretory product of the amino acid metabolism of M. dubius. Possible metabolic pathways and suggestions for the significance of serine metabolism in this parasite are discussed.

Investigating over-dispersion; Moniliformis (Acanthocephala) and rats

An analysis of the frequency distribution of numbers of Moniliformis dubius in rats of an outbred strain of Wistar origin (CFHB) and feeding ad libitum on Oxoid 41B diet, showed that over-dispersion occurred regardless of the age and sex of the rats and the infective dose given (12, 20 or 40 cystacanths/rat). Over-dispersion was also shown to be independent of variability in the age and sex of the cystacanths given. The analysis demonstrated that the over-dispersion declined as the course of the infection proceeded. As expected, parasite survival was found to be age-dependent with female worms living longer, on average, than males, and both male and female worms living longer in rats given 12 as opposed to 20 cystacanths. Possible mechanisms for generating the over-dispersion observed during this work are discussed and a tentative hypothesis, invoking host heterogeneity with regard to carbohydrate availability in the small intestine, is proposed for further experimental investigation.

Aminergic neurons in the anterior nervous system of the rat acanthocephalan Moniliformis dubius

The cerebral ganglion and nerve tracts of Moniliformis dubius show intense, specific, green fluorescence that is also associated with the lateral and apical sensory bulbs. Radioenzymatic assays showed that high levels of dopamine were present but only small amounts of the catecholamines norepinephrine and epinephrine were identified. Incubations of the proboscis sac in dilute solutions of dopamine increased fluorescence while incubations in reserpine resulted in loss of fluorescence. Nonfluorogenic amine octopamine was also detected radioenzymatically. Neutral red vitally stained a number of cells in the cerebral ganglion and the nerve tracts extending from the ganglion. Electron microscopy showed that many neurons contained electron-dense vesicles. The close association of the fluorescing, amine-containing nerve tracts with the sensory bulbs suggests that they may play a functional role in sensory reception and transmission in M. dubius. This is the first report on the presence of biogenic amines in the Acanthocephala.

Carbohydrate transport in Moniliformis dubius (Acanthocephala). III. Post-absorptive fate of fructose, mannose, and galactose

The initial metabolism of fructose, mannose, and galactose in Moniliformis dubius (M. moniliformis; Acanthocephala) was examined following brief aerobic incubations in 14C-labeled substrate. The pattern of incorporation of radioactivity from 14C-fructose and 14C-mannose into intermediates of hexose metabolism was indistinguishable from that reported elsewhere for the initial post-absorptive metabolism of 14C-glucose under comparable conditions; these hexoses were phosphorylated rapidly following their absorption, and much of the radioactivity absorbed as mannose or fructose was recovered in the nonreducing disaccharide trehalose [alpha-D-glucopyranosyl-(1 leads to 1)-alpha-D-glucopyranoside]. 14C-Galactose was phosphorylated less readily than the other hexoses. More than half of the radioactivity absorbed as galactose was incorporated into disaccharide; some of the galactose-derived disaccharide had properties suggesting the presence of a galactosyl moiety. Incorporation of radioactivity from any of the hexoses into glycogen was minimal. The extensive incorporation of hexose moieties into trehalose or a trehalose-like disaccharide rather than glycogen underscores the probable importance of trehalose metabolism to carbohydrate assimilation in Moniliformis. Physiological factors which might favor trehalose biosynthesis over glycogenesis are considered.

Dietary relations between Moniliformis (acanthocephala) and laboratory rats

Aspects of the course of infection of Moniliformis dubius in male rats fed on four purified, isocaloric diets (A, B, C and D) were investigated. Diet A contained no digestible carbohydrate, diet B contained glycerol as a potential source of glucose, diet C contained 3.6 % starch and diet D contained about 59 % starch. After a rat had been adapted to one of the diets, it was infected orally with 20 cystacanths of Moniliformis and allowed to continue feeding on the same diet for periods varying from 1 to 18 weeks. A group of 4 rats was studied in this way on each of the diets for 11 weeks and on diets C and D for a further 7 weeks. The effects of the dietary treatments on the rats were studied by measuring their food intake, growth rate and liver glycogen. At the end of each experi­mental period, the rats were killed and the numbers, location, dry masses and state of reproduction of the worms were recorded. The composition of the diet appeared to have no effect on the establishment of Moniliformis in the small intestine and the populations of worms emigrated against the direction of gastrointestinal flow during the first month of the course of infection irrespective of the diet of the host. Worms from the rats fed on diets A and B hardly grew, their survival in their hosts did not appear to continue after 11 weeks and they showed no evidence of reproductive activity. Worms from rats fed on the low starch diet (C) did not grow as rapidly as those from rats fed on the high starch diet (D) during the first few weeks of the infection, but eventually they grew much larger and lived longer than worms from the hosts feeding on the high starch diet. Worms in the rats fed on diet C appeared to remain in a precise location in the anterior part of the small intestine from 4 weeks after infection of the host until the end of the experimental period. Worms in the rats fed on diet D had begun to move posteriorly in the small intestine from about 7 weeks after the infection of the host. The results of an experiment involving the transfer of rats with established infections of Moniliformis from a standard laboratory diet to diets A, B, C and D supported the conclusion that the survival, growth and reproduction of Moniliformis are dependent on the availability of glucose liberated during digestion in the host. Another experiment demonstrated that Moniliformis can survive periods of at least 14 days during which the host is deprived of an essential amino acid.

Carbohydrate transport in Moniliformis dubius (Acanthocephala). I. The kinetics and specificity of hexose absorption

The uptakes of 14C-glucose, -2-deoxyglucose, -mannose, -N-acetylglucosamine, -3-0-methylglucose, -fructose, and -galactose by female Moniliformis dubius were nonlinear, saturable functions of hexose concentration. Kinetic and inhibition studies indicated that glucose and 2-deoxyglucose were absorbed via a single common transport locus. Mannose, N-acetylglucosamine, 3-0-methylglucose, fructose, and galactose (in decreasing order of effectiveness) inhibited the uptake of glucose in a completely competitive manner; their absorptions appeared to be mediated by the glucose transport locus and, to some degree, by one or more additional transport systems. Kinetic studies suggested that the apparent inhibitions of 14C-glucose uptake by maltose and glucose-6-phosphate were due to free glucose liberated through the action of surface hydrolases. The uptake of 14C-glucose was also inhibited by salicin, alpha-methylglucoside, and beta-methylglucoside, but not by pentoses, L-hexoses, sugar alcohols, disaccharides (except maltose), gluconic acid, glucuronic acid, phlorizin, or ouabain. Glucose uptake was not Na+-dependent.