Hepatic microsomal NADPH-cytochrome P-450 reductase from little skate, Raja erinacea. Comparison of thermolability and other molecular properties with a mammalian enzyme

Components of little skate (an elasmobranch) and rabbit hepatic microsomal cytochrome P-450 dependent monooxygenase systems were examined for differences which might explain the decreasing xenobiotic-metabolizing activity of little skate microsomes assayed at temperatures above 30 degrees C. The proportion of saturated fatty acids in microsomal lipids and the habitat temperature are both lower in skate as compared to rabbit, which is consistent with the known adaptive pattern. The more thermolabile enzyme of the skate system in microsomal preparations is NADPH-cytochrome P-450 reductase. The optimal assay temperature for purified skate reductase (30 degrees C) is 10 degrees C lower than that for the purified rabbit reductase. The purified skate reductase differs from rabbit reductase in monomeric molecular weight, in peptides produced by partial proteolysis, in immunochemical properties, but not in flavin content.     

Comparison of distribution and metabolism between tellurium and selenium in rats

Tellurium (Te) has shown recent increase in use as a component of optical magnetic disks having phase-change property, such as digital versatile disk-random access memory (DVD-RAM) and DVD-rewritable (DVD-RW). However, the toxicity and metabolic pathway of Te remain unclear despite its being known as a non-essential and harmful metalloid. This study was performed to gain an insight into Te metabolism in the body. The mechanism for the distinction of Te from selenium (Se), an essential metalloid belonging to the same group as Te, was also clarified. Rats were given drinking water containing tellurite and ⁸²Se-labeled selenite at the same concentration, and the concentrations of these metalloids in organs, body fluid and excreta were determined 2 days later. The results demonstrate that urinary and fecal excretion of Te was, respectively, lower and higher than that of exogenous (labeled) Se, suggesting that Te was less absorbed than Se. The ingested Te was transformed, i.e., methylated in organs and effluxed into bloodstream, and the effluxed Te was highly accumulated in rat red blood cells (RBCs) in the form of dimethylated Te. In contrast, Se was not accumulated in RBCs. Finally, Te was excreted in urine as trimethyltelluronium and might be exhaled as dimethyltelluride. The results suggest that the metabolism of Te was distinct from that of Se in rats.     

Interactions between different selenium compounds and zinc, cadmium and mercury

In this paper, we present a polarographic study of systems containing different inorganic and organic selenium compounds (sodium selenite, sodium selenate, seleno-methionine and seleno-urea) and metal ions (Zn2+, Cd2+ Hg2+) of the 12th group of elements in the periodic table. While zinc is a trace element known to be essential for plants and animals, cadmium and mercury are exogenous elements and are harmful pollutants that accumulate during aging; selenium is also recognized as an important micronutrient and is sometimes added to the diet. Experiments investigating the interactions were carried out using polarographic techniques in unbuffered systems. The three metal cations originated complexes with different strength and solubility in the presence of selenite anions; in the presence of selenate, polarography was not able to detect formation of complexes with these metal ions, at least under the experimental conditions used: a decrease of Hg2+ ion concentration was observed. Seleno-methionine did not react with Cd2+; in the presence of Zn2+, a soluble complex with a co-ordination number 1 was formed, while, again, the concentration of Hg2+ decreased in the presence of increasing concentrations of the selenium derivative. Seleno-urea did not react with Zn2+, but formed a complex with Cd2+ with limited solubility. Finally, this ligand could not be studied with Hg2+ because of the overlapping of the reduction potentials of both the ligand and the metal cation. Overall equilibrium constants for complex formation (Kf) and the solubility product (Ksp) for poorly soluble species are also reported.     

Human erythrocyte hemolysis induced by selenium and tellurium compounds increased by GSH or glucose: a possible involvement of reactive oxygen species

Oxidative stress can induce complex alterations of membrane proteins in red blood cells (RBCs) eventually leading to hemolysis. RBCs represent a good model to investigate the damage induced by oxidizing agents. Literature data have reported that chalcogen compounds can present pro-oxidant properties with potent inhibitory effects on cell growth, causing tissue damage and inhibit a variety of enzymes. In this study, human erythrocytes were incubated in vitro with various chalcogen compounds at 37 °C: diphenyl ditelluride (1), dinaphthalen diteluride (2), diphenyl diselenide (3), (S)-tert-butyl 1-diselenide-3-methylbutan-2-ylcarbamate (4), (S)-tert-butyl 1-diselenide-3-phenylpropan-2-ylcarbamate (5), selenium dioxide (6) and sodium selenite (7) in order to investigate their potential in vitro toxicity. After 6 h of incubation, all the tested compounds increased the hemolysis rate, when compared to control and compound (2) had the most potent hemolytic effect. The addition of reduced glutathione (GSH) or glucose to the incubation medium enhanced hemolysis caused by chalcogen compounds. The thiol oxidase activity of these compounds was evaluated by measuring the rate of cysteine (CYS) and dithiotreitol (DTT) oxidation. DTT and cysteine oxidation was increased by all the compounds tested. The results suggest a relationship between the oxidation of intracellular GSH and subsequent generation of free radicals with the hemolysis by chalcogen compounds.     

Long-term study of ovine pulmonary adenocarcinogenesis in sheep with marginal vs. sufficient nutritional selenium supply: Results from computed tomography,pathology, immunohistochemistry,JSRV-PCR and lung biochemistry

The impact of selenium (Se) in carcinogenesis is still debatable due to inconsistent results of observational studies, recent suspicion of diabetic side effects and e.g. dual roles of glutathione peroxidases (GPx). Previously, our group introduced long-term studies on lung carcinogenesis using the jaagtsiekte sheep retrovirus (JSRV) induced ovine pulmonary adenocarcinoma (OPA) as an innovative animal model. The present report describes the results of sufficient (0.2 mg Se/kg dry weight (dw)) vs. marginal (<0.05 mg Se/kg dw) nutritional Se supply on cancer progression over a two-year period in 16 animals. Computed tomography (CT) evaluation of lung cancer progression, final pathological examination, evidence of pro-viral JSRV-DNA in lung, lymph nodes and broncho-alveolar lavage cells as well as biochemical analysis of Se, GPx1 and thioredoxin reductase (TrxR) activity in lung tissue were recorded. Additionally, immunohistochemical determination of GPx1 expression in unaffected and neoplastic lung cells was implemented.The feeding regime caused significant differences in Se concentration and GPx1 activity in lung tissue between groups, whereas TrxR activity remained unaffected. JSRV was evident in broncho-alveolar lavage cells, lung tissue and lung lymph nodes. Quarterly executed CT could not demonstrate differences in lung cancer proliferation intensity. Necropsy and histopathology substantiated CT findings. Immunohistochemical analysis of GPx1 in lung tissue suggested a coherency of GPx1 immunolabelling intensity in dependence of tumour size.It was concluded that the model proved to be suitable for long-term studies of lung cancer proliferation including the impact of modifiable nutritional factors. Proliferation of OPA was unaffected by marginal vs. sufficient nutritional Se supply.     

Age-dependent changes in cell proliferation and cell death in the periodontal tissue and the submandibular gland in mice: a comparison with other tissues and organs

This study investigated the age-dependent changes in the number of BrdU- and TUNEL-positive cells in murine gingival tissue and submandibular gland, and compared the findings with those in other tissues and organs. The cell proliferative activity was decreased after 20 weeks of age in epithelial cells of the gingiva, tongue, buccal mucosa and skin. A decreased cell proliferative activity was also associated with aging in the liver and kidney parenchymal cells. Meanwhile, cell death showed peculiar changes in gingival subepithelial tissue, and mucous and serous acini of the submandibular gland. An increase of TUNEL-positive cells was demonstrated in gingival subepithelial tissue after 20-week-old of age. A significant increase of TUNEL-positive cells was also found in the mucous acinar cells in the 20-week-old mice and in the serous acini after 20 weeks. The fluctuation in the number of TUNEL-positive cells in the subepithelial tissue of the skin, and BrdU- and TUNEL-positive staining ratios in the liver was smaller than that in other tissue and organs throughout life. This study may provide useful information for better understanding the influence of aging on the functional alteration that occurs in the gingival tissue and submandibular gland of the elderly.     

Absolute hearing thresholds and critical masking ratios in the European barn owl: a comparison with other owls

Absolute thresholds and critical masking ratios were determined behaviorally for the European barn owl (Tyto alba guttata). It shows an excellent sensitivity throughout its hearing range with a minimum threshold of −14.2 dB sound pressure level at 6.3 kHz, which is similar to the sensitivity found in the American barn owl (Tyto alba pratincola) and some other owls. Both the European and the American barn owl have a high upper-frequency limit of hearing exceeding that in other bird species. Critical masking ratios, that can provide an estimate for the frequency selectivity in the barn owl's hearing system, were determined with a noise of about 0 dB spectrum level. They increased from 19.1 dB at 2 kHz to 29.2 dB at 8 kHz at a rate of 5.1 dB per octave. The corresponding critical ratio bandwidths were 81, 218, 562 and 831 Hz for test-tone frequencies of 2, 4, 6.3 and 8 kHz, respectively. These values indicate, contrary to expectations based on the spatial representation of frequencies on the basilar papilla, increasing bandwidths of auditory filters in the region of the barn owl's auditory fovea. This increase, however, correlates with the increase in the bandwidths of tuning curves in the barn owl's auditory fovea. Accepted: 27 November 1997     

Annual net production and life span of floating leaves in Nymphaea tetragona Georgi: a comparison with other floating-leaved macrophytes

Fredericella sultana (Blumenbach, 1779) has long been considered one of the few freshwater bryozoan species with a truly cosmopolitan distribution. However, chromosome spreads from European material show 2n = 16 compared to 2n = 14 in North American specimens. In laboratory rearing the two forms are morphologically indistinguishable except for the surface texture of their statoblasts. Smooth statoblasts of European colonies match early illustrations of the species, while the densely pitted statoblasts of the North American form resemble those of F. indica Annandale 1909. On the basis of these observations we tentatively designate the North American F. sultana as F. indica. The only known American species with smooth statoblasts is F. australiensis Goddard 1909, in which the 2n = 16 karyotype is similar or identical to European F. sultana; however, despite this karyotypic similarity the two species retain their distinguishing morphology when reared together in the laboratory. Two enzymes from a single specimen of European F. sultana were electrophoretically distinct from the corresponding enzymes present in samples of both F. australiensis and North American F. sultana. Four phosphoglucose isomerase alleles were present in North American F. aultana from four geographically separated collection sites, although only one genotype for this locus was observed in material from any one site. These genetic findings are consistent with a relatively short-range dispersal potential in this species as compared to Plumatella species.     

Growth and reproduction in Canthigaster valentini (Pisces,Tetraodontidae): a comparison of a toxic reef fish with other reef fishes

Synopsis The growth and reproduction of Cantigaster valentini were studied in two sites at Lizard Island, Australia. C. valentini was found to be a gonochore, with a sex ratio very close to 1:1; sexes could be distinguished externally. The growth (in length) of known individuals from both sites was measured at least every two months over two years. Growth rates of males and females decrease as their sizes increase. Growth rates differ between sexes and between sites: males generally grow faster than females and individuals at Mermaid Cove generally grow faster than individuals at Palfrey Island. Spawning is demersal, it occurs daily between 0800 and 1600h, and continues year-round. For females the interval between successive spawnings varies from about 4 days in the warm-water season to about 10 days in the cool-water season. From a comparison of local reproductive output and local recruitment survivorship of larvae in the plankton was estimated to be much higher than in another species (Pomacentrus wardi) for which a similar estimate was available. We suggest that some aspects of the reproductive strategy of C. valentini differ from other, non-toxic reef fishes in ways consistent with a reduced threat of predation upon adults, eggs, and larvae: courtship and spawning are unhurried and occur throughout most of the day; spawning is unrelated to lunar cycles; there is no parental care or defense of fertilized eggs; and embryos often hatch on rising tides.Centre for Environmental and Urban StudiesSenior author's present address: School of Biological Sciences F07, University of Sydney, Sydney 2006, N.S.W., Australia     

Prolonged incubation with low concentrations of mercury alters energy transfer and chlorophyll (Chl) a protein complexes in Synechococcus 6301: changes in Chl a absorption and emission characteristics and loss of the F695 emission band

Synechococcus PCC 6301 cells grown in the presence of low sublethal levels of (about 2 m) mercury induced alterations in chlorophyll (Chl) a absorption without significant alterations in phycocyanin. Chl a fluorescence emission in Hg²⁺ -raised cells showed a large (about 18 nm) blue shift in the peak emission. No major spectral changes in phycobilisome (PBsome) emission characteristic were noticed, indicating major structural alterations in Chl-protein complexes by incubation with Hg²⁺ ions. Low temperature (77 K) emission spectra of cells grown in the presence of Hg²⁺ showed a loss of the characteristic Chl a emission band at 695 nm (F695), which is known to be linked to photosystem II photochemistry and to originate from the Chl a of core antenna polypeptide CP 47 of photosystem II. The SDS-PAGE polypeptide profile of thylakoids indicates a loss of a polypeptide(s) with a molecular mass between 40 and 60 k Da by Hg²⁺ incubation of cells. Our results suggest that prolonged incubation of Synechococcus 6301 cells with low concentrations of Hg²⁺ affects the Chl a spectral properties and the structure of Chl-protein complexes.     

Cardiovascular autonomic response to food ingestion in patients with gastritis: a comparison between Helicobacter pylori-positive and -negative patients

BACKGROUND: Feeding evokes a cardiovascular response associated to an increased sympathetic drive. The role of the parasympathetic component in this regard is less clear. Improvement of postprandial vasovagal complaints after Helicobacter pylori eradication in three cases led us to assess autonomic response to feeding in H. pylori-positive patients in search for an exacerbated parasympathetic response. MATERIAL AND METHODS: Patients with mild or moderate chronic histologic gastritis were studied. Subjects with the same diagnosis but testing negative for H. pylori were used as controls. Noninvasive cardiovascular tests were applied before and after feeding. RESULTS: On sympathetic tests, standing postprandial blood pressure was lower than preprandially in 5/12 H. pylori-positive patients and in 0/9 controls, p = .045. Resting postprandial BP on handgrip test was significantly lower than preprandially only in H. pylori-positive patients (71 +/- 8 versus 76 +/- 6 mmHg, p = .0068). Regarding parasympathetic tests, the 4-s unloaded exercise revealed greater initial heart rate response to unloaded cycling after feeding than preprandially again only in H. pylori-positive patients (1.40 +/- 0.20 versus 1.33 +/- 0.17, p = .0195). On tests influenced by both branches of the autonomic system, a difference was seen in the chronotropic response to handgrip. Postprandial heart rate on effort of H. pylori-positive patients was not higher than preprandially in contrast to controls [intervals between 2 consecutive R waves on electrocardiogram (R-R intervals) of 666 +/- 39 versus 685 +/- 62 ms, p = .0195], suggesting blunted sympathetic activation in the former. CONCLUSION: Supporting the observations that motivate the study, our findings indicate blunted sympathetic reactivity and exacerbated vagal response to feeding in H. pylori-positive patients.     

A comparison of patient satisfaction between treatment with conventional complete dentures and overdentures in the elderly: a literature review

doi:10.1111/j.1741‐2358.2009.00299.x
A comparison of patient satisfaction between treatment with conventional complete dentures and overdentures in the elderly: a literature review Background: It has been stated that mandibular overdentures are more satisfactory than conventional dentures, but problems relating to the use of retrospective ratings, lack of control group and sequential provision of treatment may compromise the findings. Objective: To establish a comparison between treatment with conventional complete dentures and implant‐retained overdentures in elderly patients by conducting a literature review. Materials and methods: A search of English language peer‐review literature was completed using Medline up to 2008 focusing on evidence‐based research. Randomised clinical trials (RCTs) and longitudinal prospective studies were favoured in the review, using a general hierarchical classification. Articles that did not focus exclusively on the comparison of patient satisfaction between complete dentures and overdentures were excluded from further evaluation. The last search was conducted in February 2008. Key terms included quality of life, patient satisfaction, edentulism, complete denture and overdenture. Results: Among the 90 articles found in the initial search, 27 met the inclusion criteria. This included 18 RCTs and eight prospective and one cohort study. Most of the articles stated superiority of the mandibular implant‐retained overdenture therapy over the conventional complete denture regarding patient satisfaction and quality of life. Conclusion: Even with implant treatment presenting higher patient satisfaction and improvement of quality of life, it was not possible to establish a direct comparison between the studies due to differences in adopted methodologies.     

Escape in space from enemies: a comparison between stands with and without enhanced densities of the spruce bark beetle

1 Populations of the spruce bark beetle, Ips typographus (L.), are known to grow rapidly in storm‐disturbed stands as a result of relaxation from intraspecific competition. In the present study, it was tested whether a second mechanism, escape in space from natural enemies, also contributes to the rapid population increase. 2 The experiment was conducted during the initiation phase of five local outbreaks of I. typographus triggered by a storm‐disturbance in November 1995 in southern Sweden. 3 The impact of natural enemies on the ratio of increase (number of daughters per mother) of I. typographus was compared pairwise between disturbed stands with high numbers of storm‐felled trees and undisturbed stands without wind‐felled trees. 4 Enemy impact was assessed by comparing the ratio of increase in uncaged (exposed to enemies) and caged (protected from enemies) bolts colonized by I. typographus prior to being placed in the stands. The experiment was conducted in the second and third summers after the storm‐felling. 5 Enemy impact was about twice as high in stands without wind‐felled trees compared with in stands with wind‐felled trees in the second summer whereas there was no significant difference between the stand types in the third summer. 6 The result demonstrates that spatial escape from enemies contributes to the rapid population growth of I. typographus after storm‐disturbances.     

A kinetic comparison between E2P and the E2P-like state induced by a beryllium fluoride complex in the Na,K-ATPase. Interactions with Rb+

Metal-fluoride complexes have been used to induce E2P-like states with the aim of studying the events that occur during E2P hydrolysis in P-type ATPases. In the present work, we compared the E2P-like state induced by a beryllium fluoride complex (BeF_x) with the actual E2P state formed through backdoor phosphorylation of the Na,K-ATPase. Formation of E2P and E2P-like states were investigated employing the styryl dye RH421. We found that BeF_x is the only fluorinated phosphate analog that, like Pi, increases the RH421 fluorescence. The observed rate constant, k_obs, for the formation of E2P decreases with [Pi] whereas that of E2BeF_x increases with [BeF_x]. This might wrongly be taken as evidence of a mechanism where the binding of BeF_x induces a conformational transition. Here, we rather propose that, like for Pi, binding of BeF_x follows a conformational-selection mechanism, i.e. it binds to the E2 conformer forming a complex that is much more stable than E2P, as seen from its impaired capacity to return to E1 upon addition of Na⁺. Although E2P and E2BeF_x are able to form states with 2 occluded Rb⁺, both enzyme complexes differ in that the affinity for the binding and occlusion of the second Rb⁺ is much lower in E2BeF_x than in E2P. The higher rates of Rb⁺ occlusion and deocclusion observed for E2BeF_x, as compared to those observed for other E2P-like transition and product states suggest a more open access to the cation transport sites, supporting the idea that E2BeF_x mimics the E2P ground state.     

Structural differences between the cyst walls of Streptocephalus dichotomus (Baird), S. torvicornis (Waga), and Thamnocephalus platyurus (Packard) (Crustacea: Anostraca), and a comparison with other genera and species

The surface topography and layering of the cyst wall of the fairy shrimps Streptocephalus dichotomus, S. torvicornis and Thamnocephalus platyurus are described, based on scanning electron micrographs. Cyst walls are not invariably bilayered, but may be composed of up to four layers. They are species-specific in all taxa so far studied. Cyst wall structure within single cysts may differ according to the topographical location on the cyst.     

Interactions between gangliosides and proteins in the exoplasmic leaflet of neuronal plasma membranes: A study performed with a tritium-labeled GM1 derivative containing a photoactivable group linked to the oligosaccharide chain

Interactions between gangliosides and proteins at the exoplasmic surface of the sphingolipid-enriched membrane domains can be studied by ganglioside photolabeling combined with cell surface biotin labeling. In the present paper, we report on the results obtained using a novel radioactive photoactivable derivative of GM1 ganglioside, carrying the photoactivable nitrophenylazide group at the external galactose.After cell photolabeling with the radioactive photoactivable derivative of GM1 and cell surface biotin labeling, sphingolipid-enriched domains were prepared from rat cerebellar neurons differentiated in culture and further purified by immunoprecipitation with streptavidin-coupled beads. Among proteins belonging to the sphingolipid-enriched domains that were biotin labeled, thus bearing an exoplasmic domain, a few were also cross-linked by the radioactive photoactivable ganglioside. In particular, two protein bands showing apparent molecular mass of 135 and 35 kDa were intensely photolabeled. The 135 kDa protein was immunologically identified as the GPI-anchored neural cell adhesion molecule TAG-1. These data suggest that hydrophilic interaction between the exoplasmic domains of the protein and the ganglioside sialooligosaccharide chain could exist. Published in 2004.     

Distinct diversity of KIR genes in three southern Indian populations: comparison with world populations revealed a link between KIR gene content and pre-historic human migrations

By interacting with polymorphic HLA class I molecules, the killer cell immunoglobulin-like receptors (KIR) influence the innate and adaptive immune response to infection. The KIR family varies in gene content and sequence polymorphism, thereby, distinguishing individuals and populations. To investigate KIR diversity in the earliest settlers of India, we have characterized the KIR gene content in three Dravidian-speaking populations (Mollukurumba, Kanikar, and Paravar) from the state of Tamil Nadu, southern India. The activating KIR genes and putative group-B KIR haplotypes were frequent in Paravar and Kanikar, a scenario analogous to those seen previously in other populations of Indian origin, indicating that predominance of group-B KIR haplotypes is the characteristic feature of Indian populations. In contrast, the KIR gene profile of Mollukurumba was more related to Caucasian type. It is not clear whether a local-specific selection or a recent admixture from Iran is responsible for such discrete profile in Mollukurumba. Each southern Indian population had distinct KIR genotype profile. Comparative analyses with world populations revealed that group-B KIR haplotypes were frequent in the natives of India, Australia, and America, the populations associated with those involved in extensive prehistoric human migrations. Whether or not natural selection has acted to enrich group-B KIR haplotypes in these migratory descendants is an issue that requires objective testing. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Changes in biomass and nutrient content of <Emphasis Type="Italic">Nymphoides hydrophylla</Emphasis> (Lour.) O. Kuntz. in a tropical pond: a comparison with other tropical and temperate species

A study was conducted to ascertain monthly changes in biomass of the plant and nutrient content in various organs of Nymphoides hydrophylla grown in a tropical pond during September 1999–August 2000 in relation to environmental factors. Biomass of N. hydrophylla ranged from 25 to 247 g dry weight m⁻². Among the various organs, leaf blade showed highest nitrogen (3.0–4.6%) and phosphorus content (0.9–2.4%). Comparative data of three Nymphoides species showed that N. peltata, the temperate species, had maximum potential of biomass production while long flowering period, year around growth, higher nitrogen content in various organs and presence of other associated flora were unique features of tropical species (N. hydrophylla and N. indica). Both water temperature and water level together appeared to be the best environmental variables that significantly explained the variability in biomass of N. hydrophylla.