Relationship between adrenomedullin and vasopressin-aquaporin system under general anesthesia

AIM: The roles of adrenomedullin (AM) in body fluid balance under general anesthesia were investigated. METHODS: Time course changes in plasma osmolality, AM, arginine vasopressin (AVP), and urinary aquaporin 2 (AQP2) in 17 patients undergoing abdominal surgery under general anesthesia were examined. RESULTS: Increases in plasma AM levels were observed in parallel with increases in the levels of urinary AQP2/creatinine (Cr) before induction and 90 and 180 min after initiation of anesthesia. Significant correlations between plasma AM and urinary AQP2/Cr (r = 0.62, p < 0.0001) as well as urinary AVP/Cr and AQP2/Cr (r = 0.60, p < 0.0001) were uncovered. Multivariate stepwise analysis identified plasma AM as the critical independent factor affecting urinary AQP2/Cr level. CONCLUSION: A novel correlation of AM and AQP2 which overlays an AVP-AQP2 system may play a key role in fluid homeostasis during general anesthesia.     

Metabolic flux analysis of the phenylpropanoid pathway in wound-healing potato tuber tissue using stable isotope-labeled tracer and LC-MS spectroscopy

The metabolic flux of two phenylpropanoid metabolites, N-p-coumaroyloctopamine (p-CO) and chlorogenic acid (CGA), in the wound-healing potato tuber tissue was quantitatively analyzed by a newly developed method based upon the tracer experiment using stable isotope-labeled compounds and LC-MS. Tuber disks were treated with aqueous solution of L-phenyl-d(5)-alanine, and the change in the ratio of stable isotope-labeled compound to non-labeled (isotope abundance) was monitored for p-CO and CGA in the tissue extract by LC-MS. The time-dependent change in the isotope abundance of each metabolite was fitted to an equation that was derived from the formation and conversion kinetics of each compound. Good correlations were obtained between the observed and calculated isotope abundances for both p-CO and CGA. The rates of p-CO formation and conversion (i.e. fluxes) were 1.15 and 0.96 nmol (g FW)(-1) h(-1), respectively, and for CGA, the rates 4.63 and 0.42 nmol (g FW)(-1) h(-1), respectively. This analysis enabled a direct comparison of the biosynthetic activity between these two compounds.     

Molecular cloning of a novel transmembrane protein MOLT expressed by mature oligodendrocytes

A novel oligodendrocyte (OL)-specific cDNA was isolated from brain capillary endothelial cells and characterized. The cDNA encodes a protein of 1099 amino acids that contains a signal peptide and a transmembrane domain. The protein was expressed in mature OLs in vivo and in vitro cell cultures and was thus designated as mature OL transmembrane protein (MOLT). RT-PCR analysis showed that MOLT mRNA was expressed in brain, lung, pancreas, and testis. A polyclonal antibody raised against a part of the mouse MOLT reacted specifically with multipolar OLs possessing radially oriented processes that penetrated into the gray matter. More cells were detected in the white matter, and these had longitudinally oriented processes. In a rat OL lineage culture system, oligodendrocyte precursor cells did not initially produce MOLT mRNA and protein, but when they begun to differentiate into mature OLs, they started expressing MOLT. Consequently, MOLT may function as OLs become mature and may serve as a cell-surface marker for OL differentiation.     

Mouse geminin inhibits not only Cdt1-MCM6 interactions but also a novel intrinsic Cdt1 DNA binding activity

DNA replication is controlled by the stepwise assembly of a pre-replicative complex and the replication apparatus. Cdt1 is a novel component of the pre-replicative complex and plays a role in loading the minichromosome maintenance (MCM) 2-7 complex onto chromatin. Cdt1 activity is inhibited by geminin, which is essential for the G(2)/M transition in metazoan cells. To understand the molecular basis of the Cdt1-geminin regulatory mechanism in mammalian cells, we cloned and expressed the mouse Cdt1 homologue cDNA in bacterial cells and purified mouse Cdt1 to near homogeneity. We found by yeast two-hybrid analysis that mouse Cdt1 associates with geminin, MCM6, and origin recognition complex 2. MCM6 interacts with the Cdt1 carboxyl-terminal region (amino acids 407-477), which is conserved among eukaryotes, whereas geminin associates with the Cdt1 central region (amino acids 177-380), which is conserved only in metazoans. In addition, we found that Cdt1 can bind DNA in a sequence-, strand-, and conformation-independent manner. The Cdt1 DNA binding domain overlaps with the geminin binding domain, and the binding of Cdt1 to DNA is inhibited by geminin. Taken together, we have defined structural domains and novel biochemical properties for mouse Cdt1 that suggest that Cdt1 behaves as an intrinsic DNA binding factor in the pre-replicative complex.     

Examination of morphological changes in the first formed protoxylem in Arabidopsis seedlings

We examined morphological changes in the first-formed protoxylem vessels in Arabidopsis seedlings. Between 2.5 and 8 days after imbibition, mean hypocotyl and root length increased 1.52 and 23.3 times, respectively. In the 2.5-day-old seedlings, two continuous protoxylem vessels were present in the hypocotyl-root axis. In the 8-day-old upper hypocotyls, six protoxylem vessels were observed, and in the lower hypocotyls, four protoxylem vessels and one or two metaxylem vessels were observed. In the 8-day-old roots, there were two protoxylem vessels and two or three metaxylem vessels. Two protoxylem vessels in the hypocotyls connected to two metaxylem vessels in the roots of 8-day-old seedlings. At the 0.3-mm part below the hypocotyl-root boundary, the mean intervals of neighboring annular secondary wall thickenings in protoxylem vessels in 8-day-old roots were 12.9% larger than those in 2.5-day-old roots. In more apical parts of 8-day-old roots, the mean intervals fluctuated between 1.71 and 2.29 microm. In 8-day-old seedlings, metaxylem vessels were formed between 0.4 mm above the hypocotyl-root boundary and 17 mm below the boundary. The intervals in these regions were not extended so much as protoxylem vessels were collapsed. The first-formed protoxylem vessels presumably retain their water-conductive function after metaxylem formation.     

L-Tyrosine production by Polyauxotrophic Mutants of Corynebacterium glutamicum

Polyauxotrophic mutants of Corynebacterium glutamicum which have additional requirements to L-phenylalanine were derived from L-tyrosine producing strains of phenylalanine auxotrophs, C. glutamicum KY 9189 and C. glutamicum KY 10233, and screened for L-tyrosine production. The increase of L-tyrosine production was noted in many auxotrophic mutants derived from both strains. Especially some double auxotrophs which require phenylalanine and purine, phenylalanine and histidine, or phenylalanine and cysteine produced significantly higher amounts of L-tyrosine compared to the parents, A phenylalanine and purine double auxotrophic strain LM–96 produced L-tyrosine at a concentration of 15.1 mg per ml in the medium containing 20% sucrose. L-Tyrosine production by the strain decreased at high concentrations of L-phenylalanine.