Continued divergence in VO2max of rats artificially selected for running endurance is mediated by greater convective blood O2 delivery.

We previously showed that after seven generations of artificial selection of rats for running capacity, maximal O2 uptake (VO2max) was 12% greater in high-capacity (HCR) than in low-capacity runners (LCR). This difference was due exclusively to a greater O2 uptake and utilization by skeletal muscle of HCR, without differences between lines in convective O2 delivery to muscle by the cardiopulmonary system (QO2max). The present study in generation 15 (G15) female rats tested the hypothesis that continuing improvement in skeletal muscle O2 transfer must be accompanied by augmentation in QO2max to support VO2max of HCR. Systemic O2 transport was studied during maximal normoxic and hypoxic exercise (inspired PO2 approximately 70 Torr). VO2max divergence between lines increased because of both improvement in HCR and deterioration in LCR: normoxic VO2max was 50% higher in HCR than LCR. The greater VO2max in HCR was accompanied by a 41% increase in QO2max: 96.1 +/- 4.0 in HCR vs. 68.1 +/- 2.5 ml stpd O2 x min(-1) x kg(-1) in LCR (P < 0.01) during normoxia. The greater G15 QO2max of HCR was due to a 48% greater stroke volume than LCR. Although tissue O2 diffusive conductance continued to increase in HCR, tissue O2 extraction was not significantly different from LCR at G15, because of the offsetting effect of greater HCR blood flow on tissue O2 extraction. These results indicate that continuing divergence in VO2max between lines occurs largely as a consequence of changes in the capacity to deliver O2 to the exercising muscle.     

Properties and Mode of Action of a Bactericidal Compound (= Methylglyoxal) Produced by a Mutant of Escherichia coli

A lethal product (BPG) produced by a glycerol kinase mutant of Escherichia coli was purified, and its mode of action on E. coli was studied. At concentrations where BPG strongly inhibits in vivo deoxyribonucleic acid, ribonucleic acid, and protein synthesis, it produces small effects on other functions: slight inhibition of respiration and small changes in intracellular pools of substrates, nucleic acids degradation, and adenosine triphosphate levels. BPG also inhibits in vitro protein synthesis and produces inactivation of bacteriophage T4. The bactericidal product has been identified in another laboratory as methylglyoxal (MG). By comparing BPG and MG, we confirmed this observation and concluded that the activity found in our BPG preparation is due to its MG content. We also observed that MG is able to react with guanosine triphosphate. According to these results, it is interpreted that MG could act directly on macromolecular synthesis by reacting with the guanine residues of nucleic acids and its precursors.     

The significance of the incorporation of [14C]leucine into different protein fractions by isolated ox heart mitochondria

The problem of whether isolated mitochondria are able to synthesize specific proteins was investigated, particular consideration being paid to the possible contribution of micro-organisms to this activity. With ox heart mitochondria it was shown that: (1) The medium used for the incubations inhibits the exponential phase of bacterial growth for at least 8h either in the absence or the presence of fresh mitochondria, but the inhibition disappears after 4h when mitochondria damaged by freezing and thawing are used. (2) The incorporation of [¹⁴C]leucine into total proteins is linear up to at least 8h, although part of the radioactivity at the later periods might be due to some incorporation by resting-phase bacteria. (3) A contamination by as little as 800 cells/mg of mitochondrial protein is enough to contribute substantially to the total radioactivity incorporated by the mitochondrial preparations. (4) Purified cytochrome b and cytochrome oxidase are labelled even under conditions of minimal contamination by micro-organisms (less than 60 cells/mg of mitochondrial protein) and the contribution of bacterial proteins to the radioactivity found in cytochromes is negligible, as shown by double-labelling experiments. (5) At 4h the specific radioactivities of cytochrome b and cytochrome oxidase are seven- and 16-fold lower respectively than that of a structural protein-rich fraction, suggesting that the labelling of cytochromes is due to a residual contamination by these proteins.     

Synthetic chalcones as efficient inhibitors of Mycobacterium tuberculosis protein tyrosine phosphatase PtpA

In the search for lead compounds for new drugs for tuberculosis, the activity of 38 synthetic chalcones were assayed for their potential inhibitory action towards a protein tyrosine phosphatase from Mycobacterium tuberculosis--PtpA. The compounds were obtained by aldolic condensation between aldehydes and acetophenones, under basic conditions. Five compounds presented moderate or good activity. The structure-activity analysis reveals that the predominant factor for the activity is the molecule planarity/hydrophobicity and the nature of the substituents.     

Dissociation between skeletal muscle microvascular PO2 and hypoxia-induced microvascular inflammation.

Systemic hypoxia (SHx) produces microvascular inflammation in mesenteric, cremasteric, and pial microcirculations. In anesthetized rats, SHx lowers arterial blood pressure (MABP), which may alter microvascular blood flow and microvascular Po(2) (Pm(O(2))) and influence SHx-induced leukocyte-endothelial adherence (LEA). These experiments attempted to determine the individual contributions of the decreases in Pm(O(2)), venular blood flow and shear rate, and MABP to the hypoxia-induced increase in LEA. Cremaster microcirculation of anesthetized rats was visualized by intravital microscopy. Pm(O(2)) was measured by a phosphorescence-quenching method. SHx [inspired Po(2) of 70 Torr for 10 min, MABP of 65 +/- 3 mmHg, arterial Po(2) (Pa(O(2))) of 33 +/- 1 Torr] and cremaster ischemia (MABP of 111 +/- 7 mmHg, Pa(O(2)) of 86 +/- 3 Torr) produced similar Pm(O(2)): 7 +/- 2 and 6 +/- 2 Torr, respectively. However, LEA increased only in SHx (1.9 +/- 0.9 vs. 11.2 +/- 1.1 leukocytes/100 microm, control vs. SHx, P < 0.05). Phentolamine-induced hypotension (MABP of 55 +/- 4 mmHg) in normoxia lowered Pm(O(2)) to 26 +/- 6 Torr but did not increase LEA. Cremaster equilibration with 95% N(2)-5% CO(2) during air breathing (Pa(O(2)) of 80 +/- 1 Torr) lowered Pm(O(2)) to 6 +/- 1 Torr but did not increase LEA. On the other hand, when cremaster Pm(O(2)) was maintained at 60-70 Torr during SHx (Pa(O(2)) of 35 +/- 1 Torr), LEA increased from 2.1 +/- 1.1 to 11.1 +/- 1.5 leukocytes/100 microm (P < 0.05). The results show a dissociation between Pm(O(2)) and LEA and support the idea that SHx results in the release of a mediator responsible for the inflammatory response.     

Mesenteric microvascular inflammatory responses to systemic hypoxia are mediated by PAF and LTB4.

Systemic hypoxia produces a rapid microvascular inflammatory response characterized by increased reactive oxygen species (ROS) levels, leukocyte-endothelial adherence and emigration, and increased vascular permeability. The lipid inflammatory mediator leukotriene B(4) (LTB(4)) is involved in the early hypoxia-induced responses (ROS generation and leukocyte adherence). Whether other lipid inflammatory mediators participate in this phenomenon is not known. The objective of these experiments was to study the role of platelet-activating factor (PAF) in the microvascular inflammatory response to hypoxia and its potential interactions with LTB(4) in this response. Intravital microscopy was used to examine mesenteric venules of anesthetized rats. We found that WEB-2086, a PAF receptor antagonist, completely prevented the increase in ROS levels and leukocyte adherence during a brief reduction in inspired Po(2) to anesthetized rats; administration of either WEB-2086 or the LTB(4) antagonist LTB(4)-DMA attenuated leukocyte emigration and the increase in vascular permeability to the same extent during prolonged systemic hypoxia in conscious rats. Furthermore, no additive effect was observed in either response when both antagonists were administered simultaneously. This study demonstrates a role for PAF in the rapid microvascular inflammatory response to hypoxia, as well as contributions of PAF and LTB(4) to the slowly developing responses observed during sustained hypoxia. The incomplete blockade of the hypoxia-induced increases in vascular permeability and leukocyte emigration by combined administration of both antagonists indicates that factors in addition to LTB(4) and PAF participate in these phenomena.     

Starch-bound 2S proteins and kernel texture in einkorn, <Emphasis Type="Italic">Triticum</Emphasis> <Emphasis Type="Italic">monococcum</Emphasis> ssp <Emphasis Type="Italic">monococcum</Emphasis>

The starch granule proteins from 113 einkorn wheat (Triticum monococcum ssp monococcum) accessions were analyzed by acidic, polyacrylamide gel electrophoresis (A-PAGE), and two-dimensional A-PAGE x SDS-PAGE. All accessions were confirmed to contain equal amounts of two polypeptide chains corresponding to puroindoline B (Pin-B), as well as a prominent component plus a faint band corresponding to puroindoline A (Pin-A). When compared with soft-textured common wheat, “monococcum” accessions showed an increase of 3.2- and 2.7-fold in Pin-A and Pin-B levels on the starch granules, respectively. In addition, all accessions contained a novel component of the 2S super-family of seed proteins named Einkorn Trypsin Inhibitor (ETI), which was found to be encoded as a pre-protein 148 residues long. Wild-type ETI encoded by allele Eti-A ^m 1a and “valine-type” ETI encoded by allele Eti-A ^m 1b, which occurred in 107 and six einkorn accessions, respectively, were found to accumulate on starch granules as a mature protein of 121 amino acids with a hydrophobic central domain. The einkorn accessions exhibited an average SKCS index as low as −2.05 ± 11.4, which is typical of extra-soft kernels. The total surface area of starch granules in “monococcum” wheat, as determined by visual assessments in counting chambers, was estimated at 764 mm²/mg of starch, and was about 1.5 times higher than that for common wheat. The results are discussed in relation to the identification of factors that cause the extra-soft texture of einkorn kernels.     

Alveolar hypoxia,alveolar macrophages,and systemic inflammation

Diseases featuring abnormally low alveolar PO₂ are frequently accompanied by systemic effects. The common presence of an underlying inflammatory component suggests that inflammation may contribute to the pathogenesis of the systemic effects of alveolar hypoxia. While the role of alveolar macrophages in the immune and defense functions of the lung has been long known, recent evidence indicates that activation of alveolar macrophages causes inflammatory disturbances in the systemic microcirculation. The purpose of this review is to describe observations in experimental animals showing that alveolar macrophages initiate a systemic inflammatory response to alveolar hypoxia. Evidence obtained in intact animals and in primary cell cultures indicate that alveolar macrophages activated by hypoxia release a mediator(s) into the circulation. This mediator activates perivascular mast cells and initiates a widespread systemic inflammation. The inflammatory cascade includes activation of the local renin-angiotensin system and results in increased leukocyte-endothelial interactions in post-capillary venules, increased microvascular levels of reactive O₂ species; and extravasation of albumin. Given the known extrapulmonary responses elicited by activation of alveolar macrophages, this novel phenomenon could contribute to some of the systemic effects of conditions featuring low alveolar PO₂.     

Cellular senescence and organismal ageing in the absence of p21CIP1/WAF1 in ku80−/− mice

Ku80 is important in the repair of DNA double-strand breaks by its essential function in non-homologous end-joining. The absence of Ku80 causes the accumulation of DNA damage and leads to premature ageing in mice. We showed that mouse embryonic fibroblasts (MEFs) from ku80^−/− mice senesced rapidly with elevated levels of p53 and p21. Deletion of p21 delayed the early senescence phenotype in ku80^−/− MEFs, despite an otherwise intact response of p53. In contrast to ku80^−/−p53^−/− mice, which die rapidly primarily from lymphomas, there was no significant increase in tumorigenesis in ku80^−/−p21^−/− mice. However, ku80^−/−p21^−/− mice showed no improvement with respect to rough fur coat or osteopaenia, and even showed a shortened lifespan compared with ku80^−/− mice. These results show that the increased lifespan of ku80^−/− MEFs owing to the loss of p21 is not associated with an improvement of the premature ageing phenotypes of ku80^−/− mice observed at the organismal level.