True absorption and endogenous fecal excretion of manganese in relation to its dietary supply in growing rats

A conventional balance study with 48 male weanling rats was conducted to determine true absorption and endogenous fecal excretion of manganese (Mn) in relation to dietary Mn supply, following the procedures of a previously adapted isotope dilution technique. After 10 d on a diet with 1.5 ppm Mn, eight animals each were assigned to diets containing 1.5, 4.5, 11.2, 35, 65, or 100 ppm Mn on a dry-matter basis. Three days later, each rat was given an intramuscular⁵⁴Mn injection and kept on treatment for a balance period of 16 d. Apparent Mn absorption assessed for the final 8 d, averaged 8.6 μg/d without significant treatment effects, although Mn intake ranged from 18.6 to 1200 μg/d, in direct relation to dietary Mn concentrations. Mean fecal excretion of endogenous Mn for the six treatments was 0.9, 2.7, 7.4, 11.0, 16.3, and 17.7 μg/d, respectively. These values delineate the rates to which true absorption exceeded apparent rates. True absorption, as percent of Mn intake, averaged 28.7, 15.9, 11.7, 6.1, 3.4, and 2.0, respectively, as compared with mean values of 23.9, 10.9, 6.2, 3.4, 1.2, and 0.5 for percent apparent absorption. It was concluded that both true absorption and endogenous fecal excretion markedly responded to Mn nutrition and that the reduction in the efficiency of true absorption was quantitatively the most significant homeostatic response for maintaining stable Mn concentrations in body tissues.     

Directional control and the functional organization of defensive responses inAplysia

Noxious cutaneous stimulation of anterior sites on Aplysia californica causes withdrawal and turning followed by escape locomotion. Stimulation of anterior sites causes significantly larger turning responses than does stimulation of posterior sites, so that escape locomotion is always directed away from a site of 'attack'. Later phases of escape locomotion are often the same, regardless of the site of the triggering stimulus. The defensive secretions, ink and opaline, are directed along the anterior-posterior axis at the source of noxious stimulation. Ink and opaline ejections are directed to the front or back of the animal by characteristic responses of the siphon, mantle, and parapodia. Ink and opaline are ejected by a series of coordinated pumping movements of the mantle, gill, and parapodia that closely resemble triggered 'respiratory pumping' or 'Interneuron II' episodes (Kupfermann and Kandel 1969; Byrne and Koester 1978; Hening 1982). The directed ejection of secretions from the mantle cavity in response to noxious stimulation suggests a number of potential defensive functions for these secretions including aggressive retaliation, startle display, diversion, and alarm signalling (Edmunds 1975). Taken together, our results and others' suggest an integrated scheme for the functional organization of overt defensive behavior in Aplysia, and begin to suggest testable hypotheses about the integration of defensive responses on the cellular level in this animal.     

Trypanosoma cruzi: 4-aminopyrazolopyrimidine in the treatment of experimental Chagas' disease

An allopurinol metabolite, 4-aminopyrazolopyrimidine, was tested on two different strains of mice (NMRI-IVIC and C57Bl/6J) that had been infected 4 days earlier with the virulent Ya strain of Trypanosoma cruzi. Low doses of 4-aminopyrazolopyrimidine (0.125-0.500 mg/kg body wt/day) for 10 days induced a significant reduction in parasitemia (direct counts and subinoculation experiments) and increased survival time (without any evidence of toxicity) compared with untreated animals. When tested in vitro, 4-aminopyrazolopyrimidine was sixfold more active than allopurinol as a trypanostatic drug. The low therapeutic doses of 4-aminopyrazolopyrimidine suggest that this drug may be useful in the treatment of acute Chagas' disease.     

In vitro and in vivo regulation of chloroplast glyceraldehydes-3-phosphate dehydrogenase isozymes from Chenopodium rubrum. I. Purification and properties of isozymes

Chloroplast glyceraldehyde-3-phosphate dehydrogenase (GPD, EC 1.2.1.13) was purified from leaves of Chenopodium rubrum L. Aggregated (≥ 10⁶) and disaggregated (165 × 10³) molecular weight forms were obtained by gel filtration in the presence of NAD⁺ and NADP⁺, respectively. The disaggregated enzyme was separated into two isozymes by inverse ammonium sulphate gradient solubilization: "NADP-GPD I" was homotetrameric (subunit molecular weight 39 × 10³); "NADP-GPD II" was heterotetrameric (subunit molecular weights 39 × 10³ and 43 × 10³). Isoelectric focusing of the isozymes, both aggregated and disaggregated, revealed two isoelectric forms in each case, at 4.3 and 7.7. Chloroplast GPD was "NADP-suppressed" in crude extracts due to partial oxidation, incubation with dithioerythritol restored full activity.     

Aspects of the ecology and energetics of the egg sac parasites of the wolf spider Pardosa lugubris (Walckenaer)

Summary The egg sacs of the wolf spider Pardosa lugubris are parasitised by two ichneumonid wasps, namely Gelis micrurus and Hidryta sordidus. The parasites are bivoltine, the first generation parasitising the summer egg sac of P. lugubris and the second generation parasitising, and overwintering in, the autumn egg sac. Parasitised egg sacs have a characteristic appearance.The degree of egg sac parasitism was 9.8% and 6.9% for the two egg sac batches in 1965 and 2.9% and 34.8% for those of 1966. The degree of parasitism varies from area to area as does the percentage parasitism attributable to the two species.The gross growth efficiency for Hidryta from the first egg sac is 31.2% and from the second 16.2%. 3.0% in 1965 and 4.3% in 1966, of the annual yield from P. lugubris to predators and parasites, goes to the egg sac parasites. This represents reductions in recruitment of 9.1% in 1965 and 10.9% in 1966.     

STUDIES ON CHLOROPLAST DEVELOPMENT AND REPLICATION IN EUGLENA : I. Vitamin B12 and Chloroplast Replication

When Euglena gracilis is grown under vitamin B₁₂ deficiency conditions, the amount of protein and of chlorophyll per cell increase with decrease of B₁₂ in the medium and consequently in the cell. The increase in cell protein is proportional to and precedes an increase in the number of chloroplasts per cell. This replication of the chloroplasts under deficiency conditions is not accompanied by nuclear or cell division. It is concluded that chloroplast replication in Euglena gracilis is independent of nuclear and cellular replication, at least under B₁₂ deficiency conditions. We established a graph of the growth of Euglena under different concentrations of vitamin B₁₂ added to the growth medium, which permitted us to calculate that at least 22,000 molecules of vitamin B₁₂ per cell are required to give normal growth.