Effect of stress,adrenalectomy and changes in glutathione metabolism on rat kidney metallothionein content: comparison with liver metallothionein

Eighteen hours of immobilization stress, accompanied by food and water deprivation, increased liver metallothionein (MT) but decreased kidney MT levels. Food and water deprivation alone had a significant effect only on liver MT levels. In contrast, stress and food and water deprivation increased both liver and kidney lipid peroxidation levels, indicating that the relationship between MT and lipid peroxidation levels (an index of free radical production) is unclear. Adrenalectomy increased both liver and kidney MT levels in basal conditions, whereas the administration of corticosterone in the drinking water completely reversed the effect of adrenalectomy, indicating an inhibitory role of glucocorticoids on MT regulation in both tissues. Changes in glutathione (GSH) metabolism produced significant effects on kidney MT levels. Thus, the administration of buthionine sulfoximine, an inhibitor of GSH synthesis, decreased kidney GSH and increased kidney MT content, suggesting that increased cysteine pools because of decreased GSH synthesis might increase kidney MT levels through an undetermined mechanism as it appears to be the case in the liver. However, attempts to increase kidney MT levels by the administration of cysteine or GSH were unsuccesful, in contrast to what is known for the liver. The present results suggest that there are similarities but also substantial differences between liver and kidney MT regulation in these experimental conditions.     

Recombination-deficient mutants of Salmonella typhimurium are avirulent and sensitive to the oxidative burst of macrophages

Mutations in the genes recA and recBC were constructed in the virulent Salmonella typhimurium strain 14028s. Both the recA and recBC mutants were attenuated in mice. The mutants were also sensitive to killing by macrophages in vitro. The recombination mutants were no longer macrophage sensitive in a variant line of J774 macrophage-like cells that fail to generate superoxide. This suggests that repair of DNA damage by Salmonella is necessary for full virulence in vivo and that the oxidative burst of phagocytes is one source of such DNA damage.     

Welcome aboard: are birds migrating across the Mediterranean Sea using ships as stopovers during adverse weather conditions?

Birds use stopovers during migration to interrupt endurance flight in order to minimize immediate and/or future fitness costs. Stopovers on ships is considered an exceptional and anecdotal event in the ornithological literature. This does not match the experience we had in the summer of 2021, during an oceanographic campaign in the Central Mediterranean, when we regularly observed on average 2.8 birds, of at least 13 species, stopping on board during the 25 days of the campaign. The median stopping time was 42 min, ranging from a few minutes to overnight stays on board. The probability of finding a bird stopping aboard increased with wind force and cloud cover. Birds also stopped more often in a headwind and did not stop when the wind came from different directions other than the headwind. The Central Mediterranean is one of the busiest sea routes in the world, combining the mean daily number of birds on board with the thousands of ships that pass through it during the 3 months of summer migration; we estimate that nearly 4 million birds could use ships as stopover sites. This behaviour may represent a modern-day strategy that uses ships as stopovers in the event of adverse weather conditions or could act as an ecological trap, increasing the mortality of migrants. This phenomenon deserves more research attention and further studies recording body condition and tagging of individuals on board would be informative.     

Tissue distribution of bupivacaine enantiomers in sheep

rac-Bupivacaine HCl was infused intravenously to constant arterial blood drug concentrations in sheep using a regimen of 4 mg/min for 15 min followed by 1 mg/min to 24 h. At 24 h, arterial blood was sampled, the animal was killed with a bolus of KCl solution, then rapidly dissected and samples were obtained from heart, brain, lung, kidney, liver, muscle, fat, gut, and rumen. Tissue:blood distribution coefficients for (+)-(R)-bupivacaine exceeded those of (?)-(S)-bupivacaine (P < 0.05) for heart, brain, lung, fat, gut, and rumen by an overall mean of 43%. Blood:plasma distribution coefficients of (?)-(S)-bupivacaine exceeded those of (+)-(R)-bupivacaine by a mean of 29% and this offset the tissue:blood distribution coefficients so that the previously significant enantioselective differences disappeared. It is concluded that although enantioselectivity of bupivacame distribution is shown by the measured tissue:blood distribution coefficients, it is not shown when tissue:plasma water distribution coefficients are calculated, suggesting that there is no intrinsic difference between the bupivacaine enantiomers in tissue affinity. Sheep given fatal intravenous bolus doses of rac-bupivacaine had significantly greater concentrations of (+)-(R)-bupivacaine than (?)-(S)-bupivacaine in brain (P = 0.028) and ventricle (P = 0.036); these could augment the greater myocardial toxicity of this enantiomer found in vitro. © 1993 Wiley-Liss, Inc.     

Zymosan-induced luminol-amplified chemiluminescence of whole blood phagocytes in experimental and human hyperthyroidism

Luminol-amplified CL of whole blood phagocytes was studied in rats given 3 consecutive doses of 0.1 mg L-triiodothyronine T₃/kg or in hyperthyroid patients, after stimulation by zymosan. In both cases, CL was significantly increased, in effect which was produced independently of the opsonization of the zymosan particles and markedly inhibited by azide. The in vitro addition of T₃ or L-thyroxine (T₄) to whole blood phagocytes from normal rats did not modify the opsonized zymosan-dependent CL, when assayed at the concentrations found in eutrhyroid subjects or in hyperthyroid patients. Administrations of propylthiouracil (400 mg/day for 2–3 months) to hyperthyroid patients reduced the CL response observed prior to treatment, to values comparable to those found in the euthyroid group. These data indicate that hyperthyroidism elicits an enhanced respiratory burst activity of whole blood phagocytes, probably related to adaptive changes induced by thyroid hormone on the mieloperoxidase-H₂O₂ system, rather than to direct actions of the hormone molecule or changes in the opsonic capacity of plasma.     

A chromosome-level genome assembly enables the identification of the follicule stimulating hormone receptor as the master sex-determining gene in the flatfish Solea senegalensis

Sex determination (SD) shows huge variation among fish and a high evolutionary rate, as illustrated by the Pleuronectiformes (flatfishes). This order is characterized by its adaptation to demersal life, compact genomes and diversity of SD mechanisms. Here, we assembled the Solea senegalensis genome, a flatfish of great commercial value, into 82 contigs (614 Mb) combining long- and short-read sequencing, which were next scaffolded using a highly dense genetic map (28,838 markers, 21 linkage groups), representing 98.9% of the assembly. Further, we established the correspondence between the assembly and the 21 chromosomes by using BAC-FISH. Whole genome resequencing of six males and six females enabled the identification of 41 single nucleotide polymorphism variants in the follicle stimulating hormone receptor (fshr) consistent with an XX/XY SD system. The observed sex association was validated in a broader independent sample, providing a novel molecular sexing tool. The fshr gene displayed differential expression between male and female gonads from 86 days post-fertilization, when the gonad is still an undifferentiated primordium, concomitant with the activation of amh and cyp19a1a, testis and ovary marker genes, respectively, in males and females. The Y-linked fshr allele, which included 24 nonsynonymous variants and showed a highly divergent 3D protein structure, was overexpressed in males compared to the X-linked allele at all stages of gonadal differentiation. We hypothesize a mechanism hampering the action of the follicle stimulating hormone driving the undifferentiated gonad toward testis.     

Rapid identification of Vibrio anguillarum by Colony hybridization

A 562 base pair fragment of DNA from a serotype A strain of Vibrio anguillarum was cloned into pUC9 and used as a hybridization probe for the rapid identification of Vibrio anguillarum by colony hybridization. The probe was tested on nine different fish pathogens, 15 Vibrio isolates, 2 organisms closely related to Vibrio, and 9 serotypes of V. anguillarum. The probe hybridized only with the DNA of V. anguillarum serotypes A and H. The sequence of the 562 nucleotides have been determined. This probe allows rapid, reliable, and specific detection of V. anguillarum in freshwater ayu, Plecoglossus altivelis.     

MITOCHONDRIAL-DNA ANALYSES AND THE ORIGIN AND RELATIVE AGE OF PARTHENOGENETIC LIZARDS (GENUS CNEMIDOPHORUS). III. C. VELOX AND C. EXSANGUIS

Mitochondrial DNAs (mtDNAs) of two unisexual, parthenogenetically reproducing species of whiptail lizards (Cnemidophorus velox and C. exsanguis) and their bisexual relatives were compared by restriction-enzyme analysis to assess levels of mtDNA variation and to establish the maternal ancestry of the unisexuals. No cleavage-site differences were found to be diagnostic between C. velox and C. exsanguis mtDNAs, suggesting an ancestry rooted in the same maternal lineage. The mtDNA of the unisexuals is relatively homogeneous, indicating that these lineages are of recent origin. Phylogenetic analysis revealed that the maternal ancestor of both C. velox and C. exsanguis was most probably C. burti stictogrammus, C. costatus barrancorum, or an unidentified taxon closely related to them. In addition, the mtDNA analyses demonstrate conclusively that the triploid species C. velox could not have been formed by the fertilization of an unreduced (diploid) C. inornatus egg, further strengthening the hypothesis that parthenogenesis in Cnemidophorus results from hybridization.     

THE DISTRIBUTION OF LIFE-HISTORY VARIATION IN THE DAPHNIA PULEX COMPLEX

In the midwestern United States the Daphnia pulex complex consists of a mosaic of sexual and asexual populations, providing a useful model system for studying the evolutionary forces underlying the maintenance of sex. One asexual and two sexual populations were surveyed for genetic variation for isozymes, mitochondrial DNA, and life-history characters. While the sexual populations exhibited substantial levels of genetic variance for fitness characters, no variation was detected in the asexual population at any level. However, a parallel survey among asexual clones derived from other ponds revealed large amounts of quantitative variation among clones, even among those with the same molecular profile. As a group, the asexuals are more variable for life histories than are the sexual populations. The molecular data indicate a relatively recent origin for the extant asexual D. pulex. The polyphyletic origin of these clones, combined with their microevolutionary potential, provides an explanation for their broad geographic distribution. The distribution of sex in the complex cannot be explained with the standard models that assume an invariant asexual population in reproductive isolation from the parental species. Although the frequency of asexuality may be driven by the spread of a sex-limited meiosis suppressor through sexual populations, the complete displacement of sexuality may be prevented by ecological distinctions between the two classes of individuals. On average, the asexuals are larger but produce smaller clutches than the sexuals.     

Total chemical synthesis and NMR characterization of the glycopeptide tx5a, a heavily post-translationally modified conotoxin, reveals that the glycan structure is alpha-D-Gal-(1-->3)-alpha-D-GalNAc.

The 13-amino acid glycopeptide tx5a (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* = 6-bromotryptophan and Thr* = Gal-GalNAc-threonine), isolated from Conus textile, causes hyperactivity and spasticity when injected intracerebral ventricularly into mice. It contains nine post-translationally modified residues: four cysteine residues, two gamma-carboxyglutamic acid residues, and one residue each of 6-bromotryptophan, 4-trans-hydroxyproline and glycosylated threonine. The chemical nature of each of these has been determined with the exception of the glycan linkage pattern on threonine and the stereochemistry of the 6-bromotryptophan residue. Previous investigations have demonstrated that tx5a contains a disaccharide composed of N-acetylgalactosamine (GalNAc) and galactose (Gal), but the interresidue linkage was not characterized. We hypothesized that tx5a contained the T-antigen, beta-D-Gal-(1-->3)-alpha-D-GalNAc, one of the most common O-linked glycan structures, identified previously in another Conus glycopeptide, contalukin-G. We therefore utilized the peracetylated form of this glycan attached to Fmoc-threonine in an attempted synthesis. While the result-ing synthetic peptide (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* =6-bromotryptophan and Thr* = beta-D-Gal-(1-->3)-alpha-D-GalNAc-threonine) and the native peptide had almost identical mass spectra, a comparison of their RP-HPLC chromatograms suggested that the two forms were not identical. Two-dimensional 1H homonuclear and 13C-1H heteronuclear NMR spectroscopy of native tx5a isolated from Conus textile was then used to determine that the glycan present on tx5a indeed is not the aforementioned T-antigen, but rather alpha-D-Gal-(1-->3)-alpha-D-GalNAc.