Water ingestion affects orthostatic challenge-induced blood pressure and heart rate responses in young healthy subjects: gender implications

Evidence exists that women have lower orthostatic tolerance than men during quiescent standing. Water ingestion has been demonstrated to improve orthostatic tolerance in patients with severe autonomic dysfunction. We therefore sought to test the hypothesis that water ingestion would improve orthostatic tolerance in healthy young women more than in aged-matched men. Thirty seven (22 men and 15 women) healthy subjects aged 22.5± 1.7 and 21.5±1.4 (means±SD) respectively, ingested 50ml (control) and 500ml of water 40min before orthostatic challenge on two separate days of appointment in a randomized controlled, cross-over design. Seated and standing blood pressure and heart rate were determined. Orthostatic tolerance was assessed as the time to presyncope during standing. Ingesting 500ml of water significantly improves orthostatic tolerance by 22% (32.0 ± 5.2 vs 26.2 ± 2.4min; p< 0.05) in men and by 33% (24.2±2.8 vs 18.3 ± 3.2; p< 0.05) in women. Thirty minutes after ingesting 500ml of water, seated systolic blood pressure, diastolic blood pressure, pulse pressure and mean arterial pressure rose significantly in men while only systolic blood pressure and pulse pressure rose significantly in women. However ingesting 500ml of water did not have significant effect on seated heart rate in both men and women. Ingestion of 500ml of water significantly attenuated both the orthostatic challenge-induced increased heart rate and decreased pulse pressure responses especially in women. Diastolic blood pressure tended to be positively correlated with orthostatic tolerance strongly in men than in women. Pulse pressure correlated positively while heart rate correlated negatively to orthostatic tolerance in women but not in men independent of other correlates. Water ingestion is associated with orthostatic tolerance strongly in women but weakly in men independent of other correlates. In conclusion, the findings in the present study demonstrated that water ingestion caused improvement strongly in young women than in young men. This improvement is associated with increased pulse pressure and decreased tachycardiac responses during orthostatic challenge. Keywords: Gender, Heart rate, orthostatic challenge, Pulse pressure, Water ingestion.     

DNA double-strand breaks induce deletion of CTG.CAG repeats in an orientation-dependent manner in Escherichia coli

The influences of double-strand breaks (DSBs) within a triplet repeat sequence on its genetic instabilities (expansions and deletions) related to hereditary neurological diseases was investigated. Plasmids containing 43 or 70 CTG.CAG repeats or 43 CGG.CCG repeats were linearized in vitro near the center of the repeats and were transformed into parental, RecA-dependent homologous recombination-deficient, or RecBC exonuclease-deficient Escherichia coli. The resulting repair process considerably increased deletion of the repeating sequence compared to the circular DNA controls. Unexpectedly, the orientation of the insert relative to the unidirectional ColE1 origin of replication affected the amount of instability generated during the repair of the DSB. When the CTG strand was the template for lagging-strand synthesis, instability was increased, most markedly in the recA- strain. Results indicated that RecA and/or RecBC might play a role in DSB repair within the triplet repeat. Altering the length, orientation, and sequence composition of the triplet repeat suggested an important role of DNA secondary structures during repair intermediates. Hence, we hypothesize that ColE1 origin-dependent replication was involved during the repair of the DSB. A model is presented to explain the mechanisms of the observed genetic instabilities.     

Antimicrobial egg cleaning by the fringed darter (Perciformes: Percidae: Etheostoma crossopterum): implications of a novel component of parental care in fishes

Broad-spectrum antimicrobial compounds have recently been identified in the epidermal mucus of fishes and probably serve as a first line of defence against microbial pathogens. Because of the ubiquitous nature of fungi and bacteria in aquatic systems, defence against these pathogens should be required throughout the lifespan of fishes, including the egg stage. We conducted experiments on Etheostoma crossopterum (Percidae: Catonotus), the fringed darter, to determine if the presence of a guarding male inhibits microbial colonization of eggs. Based on results from a combination of in-stream experiments, in vitro microbial assays, and morphological characteristics and behaviour of breeding males, we propose that antimicrobial egg cleaning by the guarding male is an effective component of parental care in these fish. Although innate antimicrobial compounds have been identified in a variety of organisms ranging from insects to vertebrates, integration of these compounds into a species's reproductive life history has been identified only in a small number of insect species. The results from this study not only indicate that E. crossopterum males provide a novel form of vertebrate parental care, but also have implications regarding the evolution of parental care in fishes and transitional evolutionary stages from no parental care to male parental care.     

Outline of A New Approach to Evaluate Ecological Integrity of Salt Marshes

The integrity of coastal salt marshes can be determined from the extent to which they provide key ecosystem services: food and habitat for fish and wildlife, good water quality, erosion and flood control, and recreation and cultural use. An outline of a new approach for linking ecosystem services with metrics of structure and function to evaluate the ecological integrity of salt marshes is described. One main objective of the approach is to determine whether differences in structure and function can be detected among salt marshes with similar geomorphology and hydrology but different degrees of anthropogenic stress. The approach is currently being applied to salt marshes of Narragansett Bay, RI, USA. Stable nitrogen isotopic ratios of the marsh biota reflected the nitrogen sources from the adjacent watersheds and were significantly correlated with percent residential land use. Results show that plant zonation significantly ( r = —0.82; p < 0.05) relates with percent residential land use and is potentially a sensitive indicator of anthropogenic disturbance of New England salt marshes. We are currently examining species diversity, denitrification rates, and susceptibility to erosion among the sites for additional indicators of salt marsh condition. Our results to date suggest that this approach will provide the methods needed for managers to systematically monitor and evaluate the integrity of salt marshes     

Evaluation of the nuclear DNA Diffusion Assay to detect apoptosis and necrosis

We applied the nuclear DNA Diffusion Assay, described as an accurate tool to estimate apoptotic and necrotic cells [N.P. Singh, A simple method for accurate estimation of apoptotic cells, Exp. Cell Res. 256 (2000) 328-337] to tobacco root and leaf cells. In this assay, isolated nuclei are embedded in an agarose microgel on a microscope slide and low molecular-weight DNA fragments diffuse into the microgel. Exposure of the roots to hydrogen peroxide significantly increased the average nuclear area of isolated nuclei. After 4 and 24 h of recovery, all DNA damage was repaired. The data clearly demonstrate that the manifestation of diffused nuclei upon exposure to hydrogen peroxide is not the result of non-repairable apoptotic or necrotic DNA fragmentation, but represents repairable genotoxin-induced DNA damage. In contrast, treatment with the alkylating agent ethyl methanesulphonate (EMS) followed by 24 h of recovery produced a significant increase in the average nuclear area. The contribution of apoptosis to this increase cannot be excluded. Heat treatment of leaves at 50 degrees C for 1-15 min leading to necrosis, and treatment of isolated nuclei with DNase-I, which digests DNA to nucleosome-sized fragments as during apoptosis, also led to a dose-dependent increase in the nuclear area. The use of different fluorochromes (ethidium bromide, DAPI or YOYO-1) for DNA staining yielded similar results in the DNA Diffusion Assay. As all types and sizes of diffused nuclei were observed after EMS and hydrogen peroxide treatments, we were unable to differentiate, on the basis of the structure of the nuclei, between apoptotic or necrotic DNA fragmentation and other types of genotoxin-induced DNA damage in plants.     

Hydrogen sulfide induces direct radical-associated DNA damage

Hydrogen sulfide (H(2)S) is produced by indigenous sulfate-reducing bacteria in the large intestine and represents an environmental insult to the colonic epithelium. Clinical studies have linked the presence of either sulfate-reducing bacteria or H(2)S in the colon with chronic disorders such as ulcerative colitis and colorectal cancer, although at this point, the evidence is circumstantial and underlying mechanisms remain undefined. We showed previously that sulfide at concentrations similar to those found in the human colon induced genomic DNA damage in mammalian cells. The present study addressed the nature of the DNA damage by determining if sulfide is directly genotoxic or if genotoxicity requires cellular metabolism. We also questioned if sulfide genotoxicity is mediated by free radicals and if DNA base oxidation is involved. Naked nuclei from untreated Chinese hamster ovary cells were treated with sulfide; DNA damage was induced by concentrations as low as 1 micromol/L. This damage was effectively quenched by cotreatment with butylhydroxyanisole. Furthermore, sulfide treatment increased the number of oxidized bases recognized by formamidopyrimidine [fapy]-DNA glycosylase. These results confirm the genotoxicity of sulfide and strongly implicate that this genotoxicity is mediated by free radicals. These observations highlight the possible role of sulfide as an environmental insult that, given a predisposing genetic background, may lead to genomic instability or the cumulative mutations characteristic of colorectal cancer.