The synergistic effect of carbon concentration and high temperature on lipid peroxidation in Peridinium gatunense

Lipid peroxidation in Peridinium samples taken from two differentdepths in Lake Kinneret fluctuated throughout the spring withan overall increasing trend. Samples from 0.5 and 5 m showeda similar peroxidation pattern, which was maximal after thefall off in algal biomass. The rapid decline in Peridinium biomasscoincided with ambient lake temperatures of 21–23C. Fattyacid composition profiles were similar at both depths, althoughafter the peak of the bloom, a significant increase in polyunsaturatedfatty acids and oleic acid was only found at 0.5 m, togetherwith a decrease in the percentage of polyunsaturated fatty acids.These effects were related to ambient light stress rather thana result of lipid peroxidation. Lake samples taken at differentperiods of the bloom and incubated at various temperatures showeddifferential peroxidation. Higher temperatures caused increasedlipid peroxidation, but this appeared to be dependent on thesampling period. Samples withdrawn from the lake at the beginningof the bloom showed little peroxidation after a 5 day incubationat 14C, room temperature (25C) or ambient lake temperature(16C) compared to mid-bloom samples in which there was a significantincrease in peroxidation when they were incubated at room temperature(25C) or ambient lake temperature (22C). Incubation at 14Cinhibited peroxidation; however, samples from mid-bloom againshowed enhanced peroxidation compared with those from the beginningof the bloom. These in situ results suggested a relationshipbetween temperature, another environmental variable during thebloom and lipid peroxidation in Peridinium. As total dissolvedinorganic carbon (DIC) concentrations fall significantly duringthe progress of the bloom and represent an important sourceof environmental stress, laboratory experiments were establishedto investigate the synergistic effect of temperature and carbonnutrition on lipid peroxidation in Peridinium cultures. Increasedtemperature alone caused a slight increase in lipid peroxidation,but this was greatly augmented by carbon limitation. Althoughcarbon limitation induced increased catalase activity, at highertemperatures activity declined after 48 h, allowing for thesubstantial increase in lipid peroxidation.     

Aphanizomenon ovalisporum (Forti) in Lake Kinneret, Israel

The filamentous cyanobacterium Aphanizomenon ovalisporum wasobserved for the first time in Lake Kinneret in August 1994and formed a prominent bloom from September through October.Aphanizomenon ovalisporum reappeared in diminished amounts inthe summer and fall of 1995. These events are the first recordof significant quantities of a potentially toxic nitrogen-fixingcyanobacterium in this lake. No definite provenance of inoculumhas been identified, although A.ovalisporum was also observedin a newly reflooded area (Lake Agmon) in the catchment. Unusuallyhigh water temperatures and low wind inputs were observed priorto and during the A.ovalisporum bloom period. These, togetherwith possibly enhanced availability of phosphorus or other growthfactors, may have contributed to the cyanobacterium growth in1994. Phosphorus limi tation, as indicated by high cellularalkaline phosphatase activity, the onset of stormy conditionsand a fall in water temperatures led to the demise of the 1994bloom. Although the A. ovalisporum bloom in 1994 had no seriousdirect impact on water quality, the continued presence of apotentially toxic cyanobacterium in Lake Kinneret, a major nationalwater supply source, is a cause for serious concern.     

The Isolation and Evaluation of Two Naturally Occurring Mild Strains of Vanilla Necrosis Potyvirus for Control by Cross-Protection

In an attempt to find mild virus strains that would cross-protect sgainst vanilla necrosis potyvirus (VNPV), Vanilla fragrans plants in Tonga were surveyed for the presence of mild or symptomless potyvirus infections. Potyviruses were detected by indirect ELISA using a commercially available portyvirus group monoclonal anibody. From 28 plants with mild or symptomless infections two portyvirus isolates, designated V1 and V3, included systemic infections in Nicotiana benthamiana following mechanical inoculation. V1, which causes a mild mottle in N. benthamiana, is serologically related to VNPV, while V3 which causes mild vein banding is serologically unrelated to VNPV. Prior inoculation with V1 protected N. benthamiana against the severe mosaic symptoms of VNPV when challenge inoculated after 14 and 21 days, but not after 7 days. When V3 was used as the protecting strain, cross-protection was observed in some, but not all plants, when chalenged with VNPV after 14 and 21 days.     

Nuclear matrix involvement in sperm head structural organization

Summary— In the sperm nuclei the DNA is packaged into a highly condensed form and is not organized into nucleosome and solenoid but is bound and stabilized mainly by the protamines that arrange the DNA in an almost crystalline state. As demonstrated for somatic cells, the sperm DNA has been reported to be organized in loop domains attached to the nuclear matrix structures. However, the possible role of the sperm head matrix in maintaining the loop organization in absence of a typical nucleosomal structures has not been fully elucidated. By using in situ nick translation at confocal and electron microscope level, we analyzed the organization of the DNAprotamine complex and its association with the sperm nuclear matrix. The data obtained indicate that the chromatin organization in sperm nuclei is maintained during the sperm condensation by means of interactions with the nuclear matrix at fixed sites. The fine stucture of sperm nucleus and of sperm nuclear matrix, investigated on sections and replicas of freeze-fractured specimens, suggests that the lamellar array, observed by freeze-fracturing in the sperm nuclei, could depend on the inner matrix which presents a regular organization of globular structures possibly involved in the maintenance of chromatin domains in highly condensed sperm nuclei also.     

Simulation of nitrogen assimilation by heterotrophic soil microbial biomass

Assimilation of N by heterotrophic soil microbial biomass is associated with decomposition of organic matter in the soil. The form of N assimilated can be either low molecular weight organic N released from the breakdown of organic matter (direct assimilation), or NH⁺₄ and NO⁻₃ from the soil inorganic N pool, into which mineralized organic N is released (mineralization immobilization turnover). The kinetics of C and N turnover in soil is quantifiable by means of computer simulation models. NCSOIL was constructed to represent the two assimilation schemes. The rate of N assimilation depends on the rate of C assimilation and microbial C/N ratio, thereby rendering it independent of the assimilation scheme. However, if any of the N forms is labeled, a different amount of labeled N assimilation will be simulated by the different schemes. Experimental data on inorganic N and ¹⁵N and on organic ¹⁵N dynamics in soils incubated with ¹⁵N added as NH⁺₄ or organic N were compared with data simulated by different model schemes. Direct assimilation could not account for the amount of ¹⁵N assimilated in any of the experimental treatments. The best fit of the model to experimental data was obtained for the mineralization immobilization turnover scheme when both NH⁺₄ and NO⁻₃ were assimilated, in proportion to their concentration in the soil.     

Preferential feeding behaviour of Daphnia magna

Preferential feeding behaviour by Daphnia magna was shown when Daphnia were fed on a mixture of ¹⁴C-labelled algae (Chlorella vulgaris or Scenedesmus quadricauda) and ³H-labelled bacteria (Escherichia coli). Daphnia consumption of bacteria was equal or higher in the presence of algae. On the other hand, in the presence of bacteria, algal consumption decreased by 40–70% compared to algal consumption in the absence of bacteria. ¹⁴C radioactive uptake was in good agreement with the chlorophyll content and demonstrates the preferential feeding behaviour of Daphnia.     

Development of a 3D Tissue‐Engineered Skeletal Muscle and Bone Co‐culture System

In vitro 3D tissue‐engineered (TE) structures have been shown to better represent in vivo tissue morphology and biochemical pathways than monolayer culture, and are less ethically questionable than animal models. However, to create systems with even greater relevance, multiple integrated tissue systems should be recreated in vitro. In the present study, the effects and conditions most suitable for the co‐culture of TE skeletal muscle and bone are investigated. High‐glucose Dulbecco's modified Eagle medium (HG‐DMEM) supplemented with 20% fetal bovine serum followed by HG‐DMEM with 2% horse serum is found to enable proliferation of both C2C12 muscle precursor cells and TE85 human osteosarcoma cells, fusion of C2C12s into myotubes, as well as an upregulation of RUNX2/CBFa1 in TE85s. Myotube formation is also evident within indirect contact monolayer cultures. Finally, in 3D co‐cultures, TE85 collagen/hydroxyapatite constructs have significantly greater expression of RUNX2/CBFa1 and osteocalcin/BGLAP in the presence of collagen‐based C2C12 skeletal muscle constructs; however, fusion within these constructs appears reduced. This work demonstrates the first report of the simultaneous co‐culture and differentiation of 3D TE skeletal muscle and bone, and represents a significant step toward a full in vitro 3D musculoskeletal junction model.     

The Impact of Variants in Four Genes: MC4R,FTO, PPARG and PPARGC1A in Overweight and Obesity in a Large Sample of the Brazilian Population

Biochemical Genetics - Obesity and overweight are worldwide public health problems with an evident genetic predisposition that is still poorly understood. In addition, great variability has been...     

Endocytosis of the non-catalytic ADAM23: Recycling and long half-life properties

A Disintegrin And Metalloprotease 23 (ADAM23) is a member of the ADAMs family of transmembrane proteins, mostly expressed in nervous system, and involved in traffic and stabilization of Kv1-potassium channels, synaptic transmission, neurite outgrowth, neuronal morphology and cell adhesion. Also, ADAM23 has been linked to human pathological conditions, such as epilepsy, cancer metastasis and cardiomyopathy. ADAM23 functionality depends on the molecule presence at the cell surface and along the secretory pathway, as expected for a cell surface receptor. Because endocytosis is an important functional regulatory mechanism of plasma membrane receptors and no information is available about the traffic or turnover of non-catalytic ADAMs, we investigated ADAM23 internalization, recycling and half-life properties. Here, we show that ADAM23 undergoes constitutive internalization from the plasma membrane, a process that depends on lipid raft integrity, and is redistributed to intracellular vesicles, especially early and recycling endosomes. Furthermore, we observed that ADAM23 is recycled from intracellular compartments back to the plasma membrane and thus has longer half-life and higher cell surface stability compared with other ADAMs. Our findings suggest that regulation of ADAM23 endocytosis/stability could be exploited therapeutically in diseases in which ADAM23 is directly involved, such as epilepsy, cancer progression and cardiac hypertrophy.     

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.