Unusual peaks of oxygen consumption under special alimentary conditions

Oxygen consumption (VO2), carbon dioxide production (VCO2), the resulting respiratory quotient (RQ), and motor activity were recorded simultaneously by an on-line computer every ten seconds during 16-20 hours in two decerebrate male rats. Being aphagic and adipsic the rats were fed twice daily by gastric intubation with a mixture of powdered milk plus sugar or plus sunflower oil (approx. 300 KJ daily) in 10-20 ml tap water. In all seven tests performed on these rats the recordings presented very steep reductions of RQ due every time to steep increases in VO2 without increases in VCO2. Mean number of VO2 peaks in all experiments was 12.4 +/- 1.8 (SE) with mean duration of 21.3 +/- 2.8 min. Two normal male rats were fed the same diet and on the same schedule: they presented similar VO2 peaks in 8 out of 12 experiments. Mean number was 8.7 +/- 1.0 with mean duration of 13.6 +/- 2.2 min. The VO2 peak periods never occurred in rats fed ad libitum. In the two normal rats oil ingestion produced more effect than sugar. It is suggested that the phenomenon could be due to a metabolic imbalance possibly of hepatic origin, more evident in decerebrate rats. VO2 peaks could be produced by enhanced ketogenesis, gluconeogenesis and/or extra-mitochondrial (peroxisomal, microsomal) oxidation.     

Spontaneous Reperfusion after In Situ Thromboembolic Stroke in Mice

Injection of thrombin into the middle cerebral artery (MCA) of mice has been proposed as a new model of thromboembolic stroke. The present study used sequential multiparametric Magnetic Resonance Imaging (MRI), including Magnetic Resonance Angiography (MRA), Diffusion-Weighted Imaging (DWI) and Perfusion-Weighted Imaging (PWI), to document MCA occlusion, PWI-DWI mismatch, and lesion development. In the first experiment, complete MCA occlusion and reproducible hypoperfusion were obtained in 85% of animals during the first hour after stroke onset. In the second experiment, 80% of animals showed partial to complete reperfusion during a three-hour follow-up. Spontaneous reperfusion thus contributed to the variability in ischemic volume in this model. The study confirmed the value of the model for evaluating new thrombolytic treatments, but calls for extended MRI follow-up at the acute stage in therapeutic studies.     

Isolation of Thiomonas thermosulfatus Strain 51, a Species Capable of Coupling Biogenic Pyritization with Chemiosmotic Energy Transduction

The precipitation of iron sulfides potentially offers enough energy and reducing power to sustain life but organisms harnessing this reaction have not to our knowledge been previously described. We isolated a bacterial strain, capable of forming the iron sulfide minerals troilite (FeS), greigite (Fe₃S₄), and pyrite (FeS₂), from subsurface, microbial mats in Mangalia, Romania. This strain, most closely related to strains of Thiomonas sp., forms pyrite only if the redox conditions remain negative (< ?60 mV), sulfides are provided continually (≈1 mM), and the concentration of iron remains low (≤ 0.08 mM) but constant. Pyrite formation by this microbial strain is proposed as an example of biologically controlled mineralization because it is controlled by uncouplers of oxidative phosphorylation, it is larger in living than in dead cells, it is additive (controlled less by the amount of cell surfaces and more by reagents), and it results in the formation of ATP. This study indicates that precipitation and crystal formation can represent an energy resource for life and provides support for the “iron-sulfide world hypothesis” regarding the early evolution of life on Earth.     

Short Communication

Anaerobic metabolism and oxygen carrying-capacity of white shrimp (Penaeus vannamei) exposed to short term (three days) and long term (two weeks) moderate hypoxia (2-2.6 mg/L) was investigated. Glucose and lactate levels in hemolymph increased under both hypoxic conditions, indicating an activation of anaerobic pathways during the two-weeks exposure period. In muscle, no differences of glucose and lactate levels were observed between the control group and the exposed groups. In animals exposed to hypoxia for two weeks, hemocyanin and copper in hemolymph were higher than in animals under normoxic conditions or exposed for three days. These results indicate that an increase in oxygen carrying-capacity in shrimp is evident only after a sustained condition of hypoxia. Copper levels in the hepatopancreas decreased in both hypoxic conditions, suggesting a mobilization of copper stores for hemocyanin synthesis. These results indicate that penaeid shrimp can tolerate moderate hypoxic conditions by physiological adaptations, such as anaerobic metabolism and increased oxygen carrying-capacity. These adaptations require an adequate dietary supply of proteins and copper for hemocyanin synthesis and of carbohydrates for anaerobic metabolism.     

The variability of different larch clone provenances on the response to the attack by its main pests and fungal diseases

A wide range of pests and diseases attacks larch, and over 3 years in an orchard in north-western Romania, the most frequently occurring were larch needle disease (Hypodermella laricis), the case-bearer (Coleophora laricella) and woolly adelgid (Adelges laricis) insects. Their attack on seven larch clones obtained through selection from different geographic populations from Romania was studied. To evaluate the attack intensity, four branches per tree were analysed in the upper, middle and lower third of the crowns in all cardinal directions. According to the position in the crown, a high attack intensity by H. laricis was recorded on the branches in the north direction. A high intensity of C. laricella attack was registered on the upper third of the crown, especially in the east, west and south directions. A positive relationship was identified between the damaged sprouts caused by the C. laricella and A. laricis attack. The differences among the reaction of the clones and the heritability coefficients illustrated that the response to the attacks had a strong genetic determinism, with resistance being clearly influenced by genotype. In addition to the identification of gene sources that are useful for larch breeding, this study offers technical information about the potential to develop efficient treatments based on the attacks on the tree crowns.     

Transglutaminase 6: a protein associated with central nervous system development and motor function

Transglutaminases (TG) form a family of enzymes that catalyse various post-translational modifications of glutamine residues in proteins and peptides including intra- and intermolecular isopeptide bond formation, esterification and deamidation. We have characterized a novel member of the mammalian TG family, TG6, which is expressed in a human carcinoma cell line with neuronal characteristics and in mouse brain. Besides full-length protein, alternative splicing results in a short variant lacking the second β-barrel domain in man and a variant with truncated β-sandwich domain in mouse. Biochemical data show that TG6 is allosterically regulated by Ca²⁺ and guanine nucleotides. Molecular modelling indicates that TG6 could have Ca²⁺ and GDP-binding sites related to those of TG3 and TG2, respectively. Localization of mRNA and protein in the mouse identified abundant expression of TG6 in the central nervous system. Analysis of its temporal and spatial pattern of induction in mouse development indicates an association with neurogenesis. Neuronal expression of TG6 was confirmed by double-labelling of mouse forebrain cells with cell type-specific markers. Induction of differentiation in mouse Neuro 2a cells with NGF or dibutyryl cAMP is associated with an upregulation of TG6 expression. Familial ataxia has recently been linked to mutations in the TGM6 gene. Autoantibodies to TG6 were identified in immune-mediated ataxia in patients with gluten sensitivity. These findings suggest a critical role for TG6 in cortical and cerebellar neurons.