Cadmium exerts its toxic effects on photosynthesis via a cascade mechanism in the cyanobacterium,Synechocystis PCC 6803

Despite intense research, the mechanism of Cd²⁺ toxicity on photosynthesis is still elusive because of the multiplicity of the inhibitory effects and different barriers in plants. The quick Cd²⁺ uptake in Synechocystis PCC 6803 permits the direct interaction of cadmium with the photosynthetic machinery and allows the distinction between primary and secondary effects. We show that the CO₂‐dependent electron transport is rapidly inhibited upon exposing the cells to 40 µm Cd²⁺ (50% inhibition in ～15 min). However, during this time we observe only symptoms of photosystem I acceptor side limitation and a build of an excitation pressure on the reaction centres, as indicated by light‐induced P700 redox transients, O₂ polarography and changes in chlorophyll a fluorescence parameters. Inhibitory effects on photosystem II electron transport and the degradation of the reaction centre protein D1 can only be observed after several hours, and only in the light, as revealed by chlorophyll a fluorescence transients, thermoluminescence and immunoblotting. Despite the marked differences in the manifestations of these short‐ and long‐term effects, they exhibit virtually the same Cd²⁺ concentration dependence. These data strongly suggest a cascade mechanism of the toxic effect, with a primary effect in the dark reactions.     

Anti-neoplastic activity of two flavone isomers derived from Gnaphalium elegans and Achyrocline bogotensis

Over 4000 flavonoids have been identified so far and among these, many are known to have antitumor activities. The basis of the relationships between chemical structures, type and position of substituent groups and the effects these compounds exert specifically on cancer cells are not completely elucidated. Here we report the differential cytotoxic effects of two flavone isomers on human cancer cells from breast (MCF7, SK-BR-3), colon (Caco-2, HCT116), pancreas (MIA PaCa, Panc 28), and prostate (PC3, LNCaP) that vary in differentiation status and tumorigenic potential. These flavones are derived from plants of the family Asteraceae, genera Gnaphalium and Achyrocline reputed to have anti-cancer properties. Our studies indicate that 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8-trimethoxy flavone) displays potent activity against more differentiated carcinomas of the colon (Caco-2), and pancreas (Panc28), whereas 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) cytototoxic action is observed on poorly differentiated carcinomas of the colon (HCT116), pancreas (Mia PaCa), and breast (SK-BR3). Both flavones induced cell death (>50%) as proven by MTT cell viability assay in these cancer cell lines, all of which are regarded as highly tumorigenic. At the concentrations studied (5-80 μM), neither flavone demonstrated activity against the less tumorigenic cell lines, breast cancer MCF-7 cells, androgen-responsive LNCaP human prostate cancer line, and androgen-unresponsive PC3 prostate cancer cells. 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8-trimethoxy flavone) displays activity against more differentiated carcinomas of the colon and pancreas, but minimal cytotoxicity on poorly differentiated carcinomas of these organs. On the contrary, 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) is highly cytotoxic to poorly differentiated carcinomas of the colon, pancreas, and breast with minimal activity against more differentiated carcinomas of the same organs. These differential effects suggest activation of distinct apoptotic pathways. In conclusion, the specific chemical properties of these two flavone isomers dictate mechanistic properties which may be relevant when evaluating biological responses to flavones.     

Decreased GABA receptor in the cerebral cortex of epileptic rats: effect of Bacopa monnieri and Bacoside-A

Abstact

Background

Gamma amino butyric acid (GABA), the principal inhibitory neurotransmitter in the cerebral cortex, maintains the inhibitory tones that counter balances neuronal excitation. When this balance is perturbed, seizures may ensue.

Methods

In the present study, alterations of the general GABA, GABA_A and GABA_B receptors in the cerebral cortex of the epileptic rat and the therapeutic application of Bacopa monnieri were investigated.

Results

Scatchard analysis of [³H]GABA, [³H]bicuculline and [³H]baclofen in the cerebral cortex of the epileptic rat showed significant decrease in B_max (P < 0.001) compared to control. Real Time PCR amplification of GABA receptor subunits such as GABA_Aά1, GABA_Aγ, GABA_Aδ, GABA_B and GAD where down regulated (P < 0.001) in epileptic rats. GABA_Aά5 subunit and Cyclic AMP responsible element binding protein were up regulated. Confocal imaging study confirmed the decreased GABA receptors in epileptic rats. Epileptic rats have deficit in radial arm and Y maze performance.

Conclusions

Bacopa monnieri and Bacoside-A treatment reverses epilepsy associated changes to near control suggesting that decreased GABA receptors in the cerebral cortex have an important role in epileptic occurrence; Bacopa monnieri and Bacoside-A have therapeutic application in epilepsy management.     

The non-synonymous SNP, R1150W, in SCN9A is not associated with chronic widespread pain susceptibility

Background

Chronic pain conditions are characterized by significant individual variability complicating the identification of pathophysiological markers. Leukocyte telomere length (TL), a measure of cellular aging, is associated with age-related disease onset, psychosocial stress, and health-related functional decline. Psychosocial stress has been associated with the onset of chronic pain and chronic pain is experienced as a physical and psychosocial stressor. However, the utility of TL as a biological marker reflecting the burden of chronic pain and psychosocial stress has not yet been explored.

Findings

The relationship between chronic pain, stress, and TL was analyzed in 36 ethnically diverse, older adults, half of whom reported no chronic pain and the other half had chronic knee osteoarthritis (OA) pain. Subjects completed a physical exam, radiographs, health history, and psychosocial questionnaires. Blood samples were collected and TL was measured by quantitative polymerase chain reaction (qPCR). Four groups were identified characterized by pain status and the Perceived Stress Scale scores: 1) no pain/low stress, 2) no pain/high stress, chronic pain/low stress, and 4) chronic pain/high stress. TL differed between the pain/stress groups (p = 0.01), controlling for relevant covariates. Specifically, the chronic pain/high stress group had significantly shorter TL compared to the no pain/low stress group. Age was negatively correlated with TL, particularly in the chronic pain/high stress group (p = 0.03).

Conclusions

Although preliminary in nature and based on a modest sample size, these findings indicate that cellular aging may be more pronounced in older adults experiencing high levels of perceived stress and chronic pain.     

Characterization of osteoblastic properties of 7F2 and UMR-106 cultures after acclimation to reduced levels of fetal bovine serum

Estrogen plays an important role in skeletal physiology by maintaining a remodeling balance between the activity of osteoblasts and osteoclasts. In an attempt to decipher the mechanism through which estrogen elicits its action on osteoblasts, experimentation necessitated the development of a culturing environment reduced in estrogenic compounds. The selected medium (OPTI-MEM) is enriched to sustain cultures under reduced fetal bovine serum (FBS) conditions and is devoid of the pH indicator phenol red, a suspected estrogenic agent. This protocol reduced the concentration of FBS supplementation to 0% through successive 24 h incubations with diminishing amounts of total FBS (1%, 0.1%, and 0%). The protocol does not appear to alter the viability, cell morphology, or osteoblast-like phenotype of 7F2 and UMR-106 cell lines when compared with control cells grown in various concentrations of FBS. Although the rate of mitotic divisions declined, the 7F2 and UMR-106 cultures continued to express osteoblast-specific markers and exhibited estrogen responsiveness. These experimental findings demonstrate that the culture protocol developed did not alter the osteoblast nature of the cell lines and provides a model system to study estrogen's antiresorptive role on skeletal turnover.     

MOLTING PHENOLOGY OF HARBOR SEALS ON TUGIDAK ISLAND, ALASKA

We documented the progression and timing of the annual molt of harbor seals on Tugidak Island, Alaska, from 1997 to 1999. In all years the timing of molting differed among age-sex classes. Yearlings molted first, subadults second, adult females third, and lastly adult males. Timing of molting was nearly identical in 1997–1998, whereas in 1999 molting occurred three to six days later for all age-sex classes except yearlings. Estimated dates when peak proportions of each age-sex class were molting ranged from 2 August (yearlings) to 2 September (adult males). The number of seals hauled out was positively related to the proportion of seals in the molt and negatively related to the proportion of seals in the postmolt. Population trend estimates, based on aerial counts conducted during a narrow window within the molting period, are likely biased toward certain age-sex classes. Statistical models used to estimate trend include covariates to help account for within-year variation in seal numbers, but do not account for compositional changes that occur during molting. Population modeling may elucidate the effects of within-year population structure on trend estimates. Monitoring molting phenology at additional sites is necessary to determine the extent of geographic variation in molting.     

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.      

DECLINES IN HARBOR SEAL (PHOCA VITULINA) NUMBERS IN GLACIER BAY NATIONAL PARK, ALASKA, 1992–2002

Glacier Bay National Park had one of the largest breeding aggregations of harbor seals in Alaska, and it is functionally the only marine reserve for harbor seals in Alaska; yet, numbers of seals in the Bay are declining rapidly. Understanding why seals in Glacier Bay are declining may clarify their minimal habitat needs. We estimated population trends using models that controlled for environmental and observer‐related factors. In 1992, 6,200 seals were counted on icebergs in a tidewater glacial fjord and at terrestrial sites; by 2002 only 2,550 seals were counted at these same haul‐outs. Numbers of non‐pups in the glacial fjord declined by 6.6%/yr (?39%/8 yr) in June and by 9.6%/yr (?63%/11 yr) in August and at all other haul‐outs by 14.5%/yr (?75%/10 yr) during August. In the glacial fjord the number of pups remained steady from 1994 to 1999 and made up an increasing proportion of seals counted (5.4%/yr), and the proportion of pups peaked at 34%–36%. The rapid declines do not appear to be due to changes in seal behavior or redistribution. The declines reinforce genetic evidence that harbor seals in Glacier Bay are demographically isolated from other populations and indicate that current management stocks need to be redefined. Changes in Glacier Bay's ecosystem and population demographic data from the glacial fjord suggest that interspecific competition and predation are likely factors in the declines.     

Response of plant species richness and primary productivity in shrublands along a north–south gradient in Europe to seven years of experimental warming and drought: reductions in primary productivity in the heat and drought year of 2003

We used a nonintrusive field experiment carried out at six sites – Wales (UK), Denmark (DK), the Netherlands (NL), Hungary (HU), Sardinia (Italy – IT), and Catalonia (Spain – SP) – along a climatic and latitudinal gradient to examine the response of plant species richness and primary productivity to warming and drought in shrubland ecosystems. The warming treatment raised the plot daily temperature by ca. 1 °C, while the drought treatment led to a reduction in soil moisture at the peak of the growing season that ranged from 26% at the SP site to 82% in the NL site. During the 7 years the experiment lasted (1999–2005), we used the pin‐point method to measure the species composition of plant communities and plant biomass, litterfall, and shoot growth of the dominant plant species at each site. A significantly lower increase in the number of species pin‐pointed per transect was found in the drought plots at the SP site, where the plant community was still in a process of recovering from a forest fire in 1994. No changes in species richness were found at the other sites, which were at a more mature and stable state of succession and, thus less liable to recruitment of new species. The relationship between annual biomass accumulation and temperature of the growing season was positive at the coldest site and negative at the warmest site. The warming treatment tended to increase the aboveground net primary productivity (ANPP) at the northern sites. The relationship between annual biomass accumulation and soil moisture during the growing season was not significant at the wettest sites, but was positive at the driest sites. The drought treatment tended to reduce the ANPP in the NL, HU, IT, and SP sites. The responses to warming were very strongly related to the Gaussen aridity index (stronger responses the lower the aridity), whereas the responses to drought were not. Changes in the annual aboveground biomass accumulation, litterfall, and, thus, the ANPP, mirrored the interannual variation in climate conditions: the most outstanding change was a decrease in biomass accumulation and an increase in litterfall at most sites during the abnormally hot year of 2003. Species richness also tended to decrease in 2003 at all sites except the cold and wet UK site. Species‐specific responses to warming were found in shoot growth: at the SP site, Globularia alypum was not affected, while the other dominant species, Erica multiflora, grew 30% more; at the UK site, Calluna vulgaris tended to grow more in the warming plots, while Empetrum nigrum tended to grow less. Drought treatment decreased plant growth in several studied species, although there were some species such as Pinus halepensis at the SP site or C. vulgaris at the UK site that were not affected. The magnitude of responses to warming and drought thus depended greatly on the differences between sites, years, and species and these multiple plant responses may be expected to have consequences at ecosystem and community level. Decreases in biodiversity and the increase in E. multiflora growth at the SP site as a response to warming challenge the assumption that sensitivity to warming may be less well developed at more southerly latitudes; likewise, the fact that one of the studied shrublands presented negative ANPP as a response to the 2003 heat wave also challenges the hypothesis that future climate warming will lead to an enhancement of plant growth and carbon sequestration in temperate ecosystems. Extreme events may thus change the general trend of increased productivity in response to warming in the colder sites.