Economical Speed and Energetically Optimal Transition Speed Evaluated by Gross and Net Oxygen Cost of Transport at Different Gradients

The oxygen cost of transport per unit distance (CoT; mL·kg^-1·km^-1) shows a U-shaped curve as a function of walking speed (v), which includes a particular walking speed minimizing the CoT, so called economical speed (ES). The CoT-v relationship in running is approximately linear. These distinctive walking and running CoT-v relationships give an intersection between U-shaped and linear CoT relationships, termed the energetically optimal transition speed (EOTS). This study investigated the effects of subtracting the standing oxygen cost for calculating the CoT and its relevant effects on the ES and EOTS at the level and gradient slopes (±5%) in eleven male trained athletes. The percent effects of subtracting the standing oxygen cost (4.8 ± 0.4 mL·kg^-1·min^-1) on the CoT were significantly greater as the walking speed was slower, but it was not significant at faster running speeds over 9.4 km·h^-1. The percent effect was significantly dependent on the gradient (downhill > level > uphill, P < 0.001). The net ES (level 4.09 ± 0.31, uphill 4.22 ± 0.37, and downhill 4.16 ± 0.44 km·h^-1) was approximately 20% slower than the gross ES (level 5.15 ± 0.18, uphill 5.27 ± 0.20, and downhill 5.37 ± 0.22 km·h^-1, P < 0.001). Both net and gross ES were not significantly dependent on the gradient. In contrast, the gross EOTS was slower than the net EOTS at the level (7.49 ± 0.32 vs. 7.63 ± 0.36 km·h^-1, P = 0.003) and downhill gradients (7.78 ± 0.33 vs. 8.01 ± 0.41 km·h^-1, P < 0.001), but not at the uphill gradient (7.55 ± 0.37 vs. 7.63 ± 0.51 km·h^-1, P = 0.080). Note that those percent differences were less than 2.9%. Given these results, a subtraction of the standing oxygen cost should be carefully considered depending on the purpose of each study.     

Molecular mimicry between a uveitopathogenic site of S-antigen and viral peptides. Induction of experimental autoimmune uveitis in Lewis rats.

S-Antigen (S-Ag) is a well characterized 45,000 m.w. photoreceptor cell protein. When injected into susceptible animal species, including primates, it induces an experimental autoimmune uveitis, a predominantly T cell-mediated autoimmune disease of the retina and uveal tract of the eye, and of the pineal gland. In this study we found an amino acid sequence homology between a uveitopathogenic site of S-Ag, several viral proteins and one additional nonviral protein. An experimental autoimmune uveitis and pinealitis was induced in Lewis rats with these different synthetic peptides, corresponding to the amino sequence of hepatitis B virus DNA polymerase, gag-pol polyprotein of Baboon endogenous virus and gag-pol polyprotein of AKV murine leukemia virus and potato proteinase inhibitor IIa, which contain three or more consecutive amino acids identical to peptide M in S-Ag. Lymph node cells from rats immunized with either peptide M or the different synthetic peptides showed a significant degree of cross-reaction. Mononuclear cells from monkeys (Macaca fascicularis) immunized with peptide M also showed significant proliferation when incubated with either peptide M or synthetic peptides as measured by in vitro lymphocyte mitogenesis assay using [3H]TdR. Based on our findings we conclude that a viral infection may sensitize the mononuclear cells that can cross-react with self proteins by a mechanism termed molecular mimicry. Tissue injury from the resultant autoantigenic event can take place in the absence of the infectious virus that initiated the immune response.     

Detection of Trp-P-1 and Trp-P-2, carcinogenic tryptophan pyrolysis products, in dialysis fluid of patients with uremia

In order to estimate the exposure levels of mutagenic and carcinogenic heterocyclic amines in humans, we developed a high-performance liquid chromatography method to detect 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in dialysis fluid of patients with uremia. Using this methods, dialysis fluid of 12 patients who had received hemodialysis treatment or continuous ambulatory peritoneal dialysis was examined. Trp-P-1 was detected in dialysate of all uremic patients (727 +/- 282 pmoles, n = 12). In patients who had been treated with continuous ambulatory peritoneal dialysis, the average amount of Trp-P-1 found in whole dialysate (6 l) per day was 710 +/- 203 pmoles (mean +/- S.D., n = 8). Moreover, Trp-P-2 could be detected in 5 out of 12 patients (206 +/- 85 pmoles, n = 5). These results indicate that patients with uremia are actually exposed to carcinogenic tryptophan pyrolysis products. The average exposure level of Trp-P-1 in uremic patients apparently exceeded 710 pmoles (150 ng) per day.     

Transport and Fixation of Inorganic Carbon during Photosynthesis in Cells of Anabaena Grown under Ordinary Air: III. Some Characteristics of the HCO3--Transport System in Cells Grown under Ordinary Air

In cells of cyanobacterium Anabaena variabilis grown under ordinaryair (low-CO₂ cells), the transport of both CO₂ and HCO₃^–was significantly enhanced by Na⁺. This effect was pronouncedas the external pH increased. When low-CO₂ cells were treatedwith an inhibitor of carbonic anhydrase (CA), only CO₂ transportbut not HCO₃^– transport, was inhibited. The initial rateof photosynthetic carbon fixation as a function of the concentrationof internal inorganic carbon (IC) was practically the same irrespectiveof whether CO₂ or HCO₃^– was externally supplied. Theseresults suggest that IC is actively transported through theplasma membrane in a form of HCO₃^– probably by some transporterand that the transmembrane Na⁺ gradient is involved in thisIC transport system. Free CO₂ may be hydrated by CA to HCO₃^–and then transported to the cells by this transporter. On the other hand, CO₂ is actively taken up by cells grown withair containing 5% CO₂ (high-CO₂ cells) though the enhancingeffect of Na⁺ was much smaller in high- CO₂ cells than in low-CO₂cells. The initial rate of fixation as a function of internal IC concentrationindicated that the rate of the carboxylation reaction of accumulatedIC is higher in I0W-CO₂ cells than in high-CO₂ cells. The studieswith ethoxyzolamide indicated that even in low-CO₂ cells, CAdoes not function inside Anabaena cells. These results suggestthat inside the low-CO₂ cells of Anabaena, some mediator(s)facilitates the transport of IC to RuBPCase. (Received January 23, 1987; Accepted April 24, 1987)     

Transport and Fixation of Inorganic Carbon during Photosynthesis of Anabaena Grown under Ordinary Air. I. Active Species of Inorganic Carbon Utilized for Photosynthesis

Inorganic carbon transport during photosynthesis of cyanobacteriumAnabaena variabilis grown under ordinary air was investigatedby supplying ¹⁴CO₂ or H¹⁴CO₃^– solution to three differentstrains. Both CO₂ and HCO₃^– were accumulated within thealgal cells. In the cell suspension from which dissolved inorganiccarbon had been depleted by pre-illumination, CO₂ was transportedand accumulated faster than HCO₃^–. When the concentrationof HCO₃^– injected into the cell suspension of A. variabilisM3 was 25 times as high as that of CO2 (the expected ratio atequilibrium at pH 7.8), the initial rates of fixation of bothinorganic carbon species were practically the same. On the otherhand, when ¹⁴CO₂ or H¹⁴CO₃^– was added under steady statephotosynthetic conditions, both carbon species were transportedat similar rates. The ratio of fixed to transported carbon measuredafter the initial 5 s was only 23–27% regardless of thecarbon species supplied. This percentage is much lower thanthat reported for Chlorella cells. ¹ To whom reprint requests should be addressed (Received June 30, 1986; Accepted December 16, 1986)     

Effects of Exogenous Amino Acids on Iron Uptake in Relation to their Effects on Photoperiodic Flowering in Lemna paucicostata 6746

The flowering of Lemna paucicostata 6746 grown on 14-h photoperiodwas enhanced by the addition of high concentrations of ironto the medium, which also increased the endogenous iron concentration.The addition of asparagine, aspartate, glutamate, -alanine,glycine or serine to the medium also increased the endogenousiron level, resulting in the promotion of flowering. In contrast,the addition of cysteine, cystine, glutamine, arginine, threonineor phenylalanine lowered the endogenous iron level, resultingin the inhibition of flowering. Glycine and asparagine added to the medium during an inductive96-h dark period did not promote iron uptake and had no effecton flowering, but when added during the subsequent 120-h lightperiod, they promoted both iron uptake and flowering response.The increase in the endogenous iron level seems to favor floraldevelopment rather than induction of photoperiodic floweringof Lemna paucicostata 6746. (Received September 8, 1986; Accepted March 31, 1987)     

Isolation and characterization of a novel 2-aminoethylphosphonyl-glycosphingolipid from the sea hare, Aplysia kurodai

A novel phosphonoglycosphingolipid named SGL-I' containing 1 mol of 2-aminoethylphosphonate residue was isolated from the skin of Aplysia kurodai using two silicic acid chromatography systems. Data obtained on methanolysis, permethylation, mild acid hydrolysis, and hydrogen fluoride treatment combined with thin-layer chromatography, gas liquid chromatography, gas chromatography-mass spectrometry, and proton magnetic resonance spectrometry showed that this glycolipid was 3-O-MeGal beta 1----3GalNAc alpha 1----3[6'-O-(2-aminoethylphosphonyl)Gal alpha 1----2]Gal beta 1----4Glc beta 1----1Ceramide. Palmitic acid, octadeca-4-sphingenine and anteiso-nonadeca-4-sphingenine are its major aliphatic components. The new glycolipid has essentially the same structure as another major phosphonoglycosphingolipid in the skin of Aplysia, SGL-II, that contains 2 mol of 2-aminoethylphosphonate residue, suggesting a metabolic relationship between the two.