Characterization of atrial natriuretic peptide in urine from rats treated with a neutral endopeptidase inhibitor.

To explore the mechanisms for the natriuretic effects of a neutral endopeptidase inhibitor, candoxatril, the concentration of atrial natriuretic peptide (ANP) and its molecular forms in the urine of Dahl salt-sensitive (S) rats were examined. Candoxatril-induced natriuresis (+120%, p less than 0.05) was associated with a marked increase in the urinary ANP excretion (+1200%, p less than 0.05). Analysis by Sephadex G-50 gel filtration revealed that molecular weight of the major fraction of immunoreactive (ir-) ANP in the plasma of candoxatril-treated Dahl S rats was 3K, whereas that in the urine was 2.5 K. Further analysis by reverse phase high performance liquid chromatography showed that ir-ANP in the plasma of Dahl S rats was alpha-rANP (1-28), while that in the urine from rats treated with candoxatril was alpha-rANP (1-25). These results indicate that candoxatril inhibits the complete degradation of ANP in the kidney, thereby increasing the amount of biologically active ANP reaching the distal nephron and contributing to natriuresis.     

Cloning and characterization of two forms of C-type natriuretic peptide receptor in rat brain.

Two similar membrane bound guanylate cyclases (GC-A and GC-B) are known as natriuretic peptide receptors, but have not been well characterized yet. In this study, we have isolated two forms of GC-B cDNA clones along with GC-A cDNA clones from rat brain. The two forms of rat GC-B differ from each other only by 75bp deletion at 3'-flanking region of the putative transmembrane domain, the shorter form lacking the nucleotide binding site by the deletion. Expression of these cDNAs on mammalian cells revealed that (1) GC-B is a specific receptor for CNP whereas GC-A is stimulated effectively both by ANP and BNP, and (2) the two forms of GC-B possess practically the same high binding affinity for CNP while the shorter form could not induce cGMP production by the binding of CNP. These data indicate that in rat brain is present the non-functional receptor for CNP caused by the short deletion.     

A restriction fragment length polymorphism (RFLP) locus of rat (Rattus norvegicus) linked to theCs-1 locus of rat linkage group XIII

A novel restriction fragment length polymorphism (RFLP) in inbred rats was revealed by Southern blot analysis with a clone arbitrarily chosen from a rat genomic library as a probe. A clone named alpha 403 showed interstrain variations in the length of the EcoRI and HindIII fragments. The EcoRI fragments were either 0.7 or 3 kb, those of HindIII were either 4.5 or 5 kb, and three types were identified as combinations of those fragments in 20 inbred rat strains. These types segregated in backcross progeny as codominant alleles. The locus for the RFLP was thus named A403. Analysis of linkage between the RFLP locus and 13 other loci reveal that the A403 locus was closely linked to the Cs-1 locus (15 +/- 5.2%), which belongs to rat linkage group XIII.     

Protein phylogeny of translation elongation factor EF-1α suggests microsporidians are extremely ancient eukaryotes

Partial regions of the mRNA encoding a major part of translation elongation factor 1 (EF-1) from a mitochondrion-lacking protozoan,Glugea plecoglossi, that belongs to microsporidians, were amplified by polymerase chain reaction (PCR) and their primary structures were analyzed. The deduced amino acid sequence was highly divergent from typical EF-1's of eukaryotes, although it clearly showed a eukaryotic feature when aligned with homologs of the three primary kingdoms. Maximum likelihood (ML) analyses on the basis of six different stochastic models of amino acid substitutions and a maximum parsimony (MP) analysis consistently suggest that among eukaryotic species being analyzed,G. plecoglossi is likely to represent the earliest offshoot of eukaryotes. Microsporidians might be the extremely ancient eukaryotes which have diverged before an occurrence of mitochondrial symbiosis. Sequence availability: The nucleotide sequence data reported here appear in the GSDB, DDBJ, EMBL, and NCBI databases with the accession number D32139     

Effect of temperature and growth phase on fatty acid composition of the psychrophilic Vibrio sp. strain no. 5710

Abstract The cellular fatty acid composition of the psychrophilic Vibrio sp. strain No. 5710 isolated from a deep-sea sediment sample was analyzed. The presence of docosahexaenoic acid (22:6) was demonstrated as found previously in other deep-sea bacteria, and the relative amount of 22:6 decreased as the growth temperature increased. A temperature shift from 10°C to 0°C resulted in a relative increase of 22:6, and an opposite shift led to a decrease. In addition, hexadecanoic acid (16:0) was found to increase as the growth temperature increased. Therefore, it is suggested that the adaptation of 5710 to the growth temperature was carried out by the changes in the relative amounts of 22:6 and 16:0. When 5710 was grown at low temperature, it increased the relative amount of 22:6 presumably to maintain membrane fluidity at that temperature. In contrast, 5710 grown at high temperature probably maintained the membrane fluidity by increasing the amount of a saturated fatty acid, 16:0. Furthermore, observation of the fatty acid compositions at mid-exponential phase and early stationary phase revealed the proportions of several fatty acids, including a major fatty acid, 9- cis -hexadecenoic acid (16:1c, palmitoleic acid), were affected by the growth phase which may be due to the physiological difference between the growth phases.     

The giant panda is closer to a bear,judged by α- and β-hemoglobin sequences

Summary Using - and -hemoglobin sequences, we made a maximum likelihood inference as to the phylogenetic relationship among carnivores, including the two pandas, giant and lesser. Molecular phylogenetic studies up to 1985 had consistently indicated that the giant panda is more closely related to the bear than to the lesser panda. In 1986, however, a contradictory tree was constructed, using hemoglobins and so on, in which the two pandas link together (Tagle et al. 1986). In contrast to that tree, our conclusion supports the close relationship between bear and giant panda. The surface impression of a close relationship between the two pandas drawn from pairwise amino acid differences is explained by a rapid rate of hemoglobin evolution in the bear compared to that in the two pandas.Offprint requests to: T. Hashimoto     

Two new species of the genusAmblyeleotris (Pisces: Gobiidae) from the Ryukyu Islands,Japan

Two new shrimp-associated gobies,Amblyeleotris yanoi sp. nov. andA. masuii sp. nov. are described on the basis of specimens from Iriomote-jima Island and Okinawa-jima Islands, Okinawa Prefecture, Japan.A. yanoi is distinguished from other members of the genus by the combination of the following characters: 14 anal fin soft rays, 19 pectoral fin rays, 97–103 longitudinal scales, a candle flame-shaped marking on the caudal fin, a very low membrane connecting the pelvic fins and absence of a ventral frenum.A. masuii differs from all other congeners by having 92–97 longitudinal scales, the length of the interpelvic connecting membrane relative to the longest pelvic fin ray (0.43–0.66), black blotches on the sides of the chin, and blue spots on the opercle and preopercle.     

Effect of dietary caffeine and zinc on the activity of antioxidant enzymes,zinc, and copper concentration of the heart and liver in fast-growing rats

The purpose of this study was to determine the relationship between concentrations of Zn and Cu and the activities of superoxide dismutase and glutathione peroxidase in the heart and liver of young rat pups whose dams were fed a diet supplemented with caffeine and/or Zn. Four groups of dams with their newborn pups were fed one of the following diets for 22 d: 20% protein basal diet; the basal diet supplemented with caffeine (2 mg/100 body wt); the basal diet supplemented with Zn (300 mg/kg diet); or the basal diet supplemented with caffeine plus Zn. The Cu levels in the livers of the pups were decreased by maternal intake of the caffeine and Zn diet. The maternal intake of the caffeine diet increased Mn-superoxide dismutase (MnSOD) activity and Cu, Zn-superoxide dismutase (CUZnSOD) in the heart of the pups. On the other hand, the activity of Cu,ZnSOD was significantly reduced in the liver of pups whose dams consumed a caffeine, Zn, or caffeine plus Zn diet. Cu, ZnSOD activity in the liver of the pups seems to be correlated with Cu levels in the tissue. Selenium-dependent glutathione peroxidase (GSH-Px) activities in the heart and liver showed no difference among the groups. The effect of dietary caffeine and/or Zn on the activity of antioxidant enzymes in the heart and liver were different in young rats. The activities of these enzymes in the heart were lower than in the liver of 22-d-old rats. Our experiments indicate that the heart has limited defenses against the toxic effects of peroxides when compared to the liver.