Effects of sand bar openings on some limnological variables in a hypertrophic tropical coastal lagoon of Brazil

This study describes the spatial and temporal dynamics of several physical, chemical and biological variables in the Grussai lagoon, and their relationship to ephemeral sand bar openings and to a constant in natura waste water input. The spatial variation in pH, dissolved oxygen, electrical conductivity, total alkalinity and nutrients (e.g. soluble reactive silicate, soluble reactive phosphate and ammonium) was associated to the anoxic and nutrient rich groundwater discharge, the development of aquatic macrophytes, the biological activities of phytoplanktonic community and the marine influence. During the period when the sand bar was closed (isolated), the lagoon water was supersaturated with dissolved oxygen and exhibited high values of pH (8–10), total alkalinity (3.000–5.000 μeq l^-1), and chlorophyll a contents (60-300 μg l^-1), and had low values of dissolved nutrients (nearly undetectable). These suggest a biological processes dominance. When the sand bar was opened, there was an enrichment with dissolved inorganic nutrients (e.g. ammonium and soluble reactive phosphorus up to 120 and 5 μM, respectively) and a decrease in pH (below 8), total alkalinity (below 3.000 μeq l^-1) and dissolved oxygen during the initial second to eight days. Subsequently there was a period when the physical and chemical characteristics of seawater prevailed. The lagoon returned chemical to the pre-opening water conditions in a few days (∼ 10–20). This quick return implies highly efficient biological mechanisms. The high levels of chlorophyll a, total nitrogen and phosphorus in the water column indicate a high eutrophication stage in the Grussai lagoon during the sand bar closed periods. This revised version was published online in July 2006 with corrections to the Cover Date.     

N-terminal amino acid sequence of an insect neurohormone, melanization and reddish coloration hormone (MRCH): heterogeneity and sequence homology with human insulin-like growth factor II

Catecholamine release from chromaffin cells in response to carbamylcholine and high K+ is transient. Monitoring intracellular free calcium ([Ca2+]i) using quin2 demonstrated a transient rise in [Ca2+]i in response to carbamylcholine. The termination of secretion due to carbamylcholine is probably a consequence of the return of [Ca2+]i to resting levels as the nicotinic receptors desensitise. Depolarisation with 55 mM K+ led to a long-lasting rise in [Ca2+]i which persisted after the secretory response had terminated. The maintained rise in [Ca2+]i appeared to be due to continued opening of verapamil-sensitive Ca2+ channels. These results suggest that inactivation of voltage-dependent Ca2+ channels does not account for the transient nature of the secretory response in chromaffin cells.     

Maturation of spermatozoa in the epididymis of the Chinese hamster

Chinese hamster spermatozoa gain their ability to move when they descend from the testis to the distal part of the caput epididymis, but it is not until they enter the corpus epididymis that they become capable of fertilizing eggs. The maturation of the spermatozoa proceeds as they further descend the tract and perhaps continues even in the vas deferens. During transit between the distal caput and proximal cauda epididymides, small membrane-limited vesicles (and tubules) appear on the plasma membrane over the acrosomes of the spermatozoa. The number of vesicles appearing on the sperm brane reaches a maximum when the spermatozoa are in the proximal cauda epididymis. It declines sharply in the distal cauda epididymis. Spermatozoa in the vas deferens are free of the vesicles. The origin, chemical nature, and functional role of the vesicles that appear on the sperm surface during epididymal transit must be the subject of further investigation.     

Behavioral responses of males to estradiol-treated females in the budgerigar (<Emphasis Type="Italic">Melopsittacus undulatus</Emphasis>)

We investigated the effects of estradiol-treated females on the behavior of male budgerigars. In comparison to control females, females given implants of estradiol showed elevated nest behavior and darker cere color, which are characteristics of breeding females. After we confirmed the efficacy of estradiol treatment on behavior and morphology, each female was paired with a male mate. Males paired with estradiol-treated females showed more courtship behavior (auditory and visual display, and courtship feeding) to their mates than males paired with control females. These data indicate that budgerigar females with a high estrogen level enhance males' courtship behavior. Since males did not show response to estradiol-treated females soon after females were introduced, effects of estradiol-treated female budgerigars may be mediated by the endocrine system, rather than wholly by the nervous system, of males. Electronic Publication     

Na+/Mg2+ transporter acts as a Mg2+ buffering mechanism in PC12 cells

Mg(2+) buffering mechanisms in PC12 cells were demonstrated with particular focus on the role of the Na(+)/Mg(2+) transporter by using a newly developed Mg(2+) indicator, KMG-20, and also a Na(+) indicator, Sodium Green. Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP), a protonophore, induced a transient increase in the intracellular Mg(2+) concentration ([Mg(2+)](i)). The rate of decrease of [Mg(2+)](i) was slower in a Na(+)-free extracellular medium, suggesting the coupling of Na(+) influx and Mg(2+) efflux. Na(+) influxes were different for normal and imipramine- (a putative inhibitor of the Na(+)/Mg(2+) transporter) containing solutions. FCCP induced a rapid increase in [Na(+)](i) in the normal solution, while the increase was gradual in the imipramine-containing solution. The rate of decrease of [Mg(2+)](i) in the imipramine-containing solution was also slower than that in the normal solution. From these results, we show that the main buffering mechanism for excess Mg(2+) depends on the Na(+)/Mg(2+) transporter in PC12 cells.     

Three-dimensional solution structure of an archaeal FKBP with a dual function of peptidyl prolyl cis-trans isomerase and chaperone-like activities

Here we report the solution structure of an archaeal FK506-binding protein (FKBP) from a thermophilic archaeum, Methanococcus thermolithotrophicus (MtFKBP17), which has peptidyl prolyl cis-trans isomerase (PPIase) and chaperone-like activities, to reveal the structural basis for the dual function. In addition to a typical PPIase domain, a newly identified domain is formed in the flap loop by a 48-residue insert that is required for the chaperone-like activity. The new domain, called IF domain (the Insert in the Flap), is a novel-folding motif and exposes a hydrophobic surface, which we consider to play an important role in the chaperone-like activity.     

Analysis of helicase gene mutations in Japanese Werner’s syndrome patients

The profile of helicase gene mutations was studied in 89 Japanese Werner’s syndrome (WRN) patients by examining the previously described mutations 1– 4 as well as a new mutation found during this study, designated mutation 5. Of 178 chromosomes (89 patients), 89 chromosomes (50%) had mutation 4, 11 (6.2%) chromosomes had mutation 1, and two chromosomes (1.1%) contained mutation 5. Mutations 2 and 3 were not observed in this patient population. The remaining 76 (42.7%) chromosomes had none of these mutations. A significant fraction of all patients (22 total patients, 24.7%) appear to be compound heterozygotes, including those carrying mutations of both types 1 and 4. The genotype analysis of the markers surrounding the WRN helicase gene strongly suggests that most of the chromosomes carrying either mutation 1 or 4 were derived from two single founders. Received: 25 July 1996 / Revised: 20 September 1996     

Localization by immunohistochemistry of renal ornithine decarboxylase in the mouse with and without testosterone treatment

The immunohistochemical distribution of renal ornithine decarboxylase was studied in male mice both with and without testosterone treatment. Testosterone (1 mg per mouse) induced a marked increase in ornithine decarboxylase activity of the mouse kidney, whereas no significant immunohistochemical difference was observed either in immunoreactivity or its localization. In intact male as well as androgen-treated mice dense ornithine decarboxylase-immunoreactive cells were observed mainly in the cortex, especially many ornithine decarboxylase-immunoreactive cells were observed in the inner portion, while a much weaker immunoreactivity was observed in the medulla. The largest number of ornithine decarboxylase-immunoreactive cells seemed to be localized in the pars recta of the proximal tubule. The immunoreactivity was not detected in all the tubular cells but scattered among them. The renal corpuscles were not immunoreactive. In each ornithine decarboxylase-immunoreactive cell, the cytoplasm showed much denser immunoreactivity than the nucleus.