The role of arctic zooplankton in biogeochemical cycles: respiration and excretion of ammonia and phosphate during summer

The study of the structural and functional properties of key components of polar marine ecosystems has received increased attention in order to better understand the ecological consequences of future sea temperature rise and seasonal ice retraction. Owing to this purpose, during the ATOS-Arctic cruise, held in July 2007 in the framework of the 2007–2008 International Polar Year, we studied the respiratory carbon demand of mesozooplankton as well as their contribution to the regeneration of inorganic nitrogen and phosphorus (NH₄-N and PO₄-P) via excretion. The studied area comprised several stations along a latitudinal gradient in the East Greenland current, plus a network of stations NW of the Svalbard islands. The specific respiratory carbon losses and phosphorus (PO₄-P) excretion rates were similar or slightly higher than some reports for Arctic mesozooplankton, but the nitrogen (NH₄-N) excretion rates were higher by a factor of 3 when compared with previous data sets. The mesozooplankton respiratory losses were equivalent to 23% of primary production, and at turn zooplankton contributed by excretion to more than 50% of the N and P required by phytoplankton. Although C:N, C:P and N:P metabolic atomic quotients almost coincided with the average Redfield’s stoichiometric ratios, the low C:N values when compared to previous reports suggested a predominance of protein-related metabolic substrates. The potential consequences of changes observed in the C:N, N:P and C:P metabolic ratios of mesozooplankton for Arctic marine ecosystems are discussed.     

Changes in the vulnerable period of the rat myocardium during hypoxia, hyperventilation and heart failure

Changes in the duration and size of the vulnerable period of the myocardium in the presence of respiratory changes were studied in acute experiments on rats. The limits of the vulnerable period were determined by directly stimulating the heart during ventilation via the enlarged respiratory dead space, during hyperventilation and during heart failure. In the control group (normal ventilation without enlargement of the dead space), the vulnerable period lasted 5.7 +/- 0.76 ms. During ventilation via the enlarged dead space, hypercapnic hypoxaemia developed and the vulnerable period was markedly prolonged (18.55 +/- 5.29 ms) by a shift of its inner limit to the left. Hyperventilation caused normoxic to hyperoxic hypocapnia and markedly reduced the duration of the vulnerable period (8.17 +/- 2.21 and 9.31 +/- 2.38 ms respectively). The vulnerable period lengthened the most in heart failure (25.46 +/- 3.93), mainly as a result of a shift of its outer limit. In all the experimental groups there was a shift of the vulnerable period to the right, which was fastest in hypercapnic hypoxaemia and slowest in hyperoxic hypocapnia. The administration of Inderal (3 mg/kg i.p.) or Arfonad (50 mg/kg i.p.) markedly shortened the vulnerable period during hypercapnic hypoxaemia (9.87 +/- 2.78 and 9.32 +/- 2.16 ms respectively), but did not block the shift. Lengthening of the vulnerable period during hypercapnic hypoxaemia was probably due to activation of sympathetic nerves via beta-adrenergic receptors.     

Enzymic synthesis ofL-Lysine fromDL-α-Amino-ε-caprolactam by new microbial strains

The production of L-lysine fromDL-α-amino-ε-caprolactam (DL-ACL) by new strains producingL-α-amino-ε-caprolactamase and aminocaprolactam racemase is described. Optimal conditions for hydrolysis ofL-ACL byCryptococcus sp. and for racemization of ACL by cells of a strain isolated in nature and identified asPseudomonas sp. were determined. Synthesis ofL-α-amino-ε-caprolactamase is induced byDL-ACL orL-lysine with the same effectivity. A positive effect of phosphates (potassium salts) on reduction of the induction lag was detected, the synthesis of this enzyme was found to be repressed by glucose and some possibilities of the reversion of this repressive effect were demonstrated. Under conditions optimal for the production of both enzymes a quantitative theoretical conversion of 10 % aqueousDL-ACL toL-lysine by a mixture of native cells in a mass ratio of 1: 2 (producer of ACL-hydrolase to producer of ACL-racemase) occurred in 8 h at 40 °C and pH 8.0     

Flora von Oesterreich-Ungarn

Ohne Zusammenfassung     

Prenatal detection of a fetus hemizygous for the fragile X-chromosome

Summary A male fetus of a pregnancy known to be at risk for X-linked mental retardation with fragile site Xq27 was found to be affected by demonstrating the marker X-chromosome in five of 180 (2.8%) of metaphases derived from amniocytes cultured in medium 199. The results were confirmed in fetal lymphocytes (25 of 86 metaphases, i.e. 29%), and fetal fibroblasts (five of 100 metaphases when cultured in medium 199, and 14 of 100 after exposure to methotrexate for 43 h).This work was supported in part by a research grant from the Deutsche Forschungsgemeinschaft     

The transition point for protein synthesis in late S-G2 may be delayed by genome bromosubstitution without affecting the time of entry into mitosis

Bromosubstitution for most of the S period in synchronous populations of Allium cepa L. meristematic cells resulted in a delay in the late S-G2 transition point where protein synthesis is needed for later mitotic entrance to occur. This retardation in the position of the transition point was not accompanied by the expected delay in the entrance into mitosis, suggesting that such protein synthesis is a requisite, but not a timer for prophase triggering.     

Iron metabolism in iron-deficient male quail

1. Male quails submitted 20 and 120 days to a low iron diet (7 ppm) were compared to female laying quails, exposed for 30 days to the same low iron regime, in order to compare the response of the iron metabolic control under a single (erythropoiesis) or a doubled (erythropoiesis and egg formation) iron demand. 2. Iron deposit in storage organs, the classical hematology and the intestinal iron absorption were analyzed in these animals. 3. In males, after 120 days, the iron deposits were reduced 50 and 75%, but hematological values (hematocrit and hemoglobin concentration) were normal, although in laying quails, after 30 days, an anemic condition was evident in both blood parameters and iron deposits, provoking an iron deficient erythropoiesis. 4. The enhancement of the intestinal iron uptake, confirms the anemic character of these birds.     

The spread of somatosensory-evoked potentials within the nervous system

Four thalamic and cortical recordings were carried out in 5 patients. The thalamic-evoked potentials were typical and revealed a triphasic complex, but their latencies showed a relatively high standard deviation. They could be divided into two groups according to their latencies, both of which had low SD. These data suggested that there could be two types of latency of thalamic SEP, because the 4 patients' body sizes were very similar. More detailed surface, cortical and depth recordings are needed to resolve these questions.